6.1 - Modal Verbs

Modal Verbs

English Grammar

Modal verbs are a part of the larger category called auxiliary verbs which are verbs that cannot be used on their own. They need to be accompanied by another (main) verb. Sometimes modal verbs are called modal auxiliaries.

The following words are modal verbs: Can, Could, May, Might, Must, Shall, Should, Will, Would.

They are modal auxiliary verbs that provide additional information about the verb that follows it.

Modal verbs are used to express ability, obligation, permission, assumptions, probability and possibility, requests and offers, and advice. Each modal verb can have more than meaning which depends on the context of that sentence (or question).

• You can go now. (= permission)
• I can play the guitar. (= ability)

Structure with Modal Verbs

A Modal verb is followed by another verb in the base form (the infinitive without the 'To') and they are not conjugated (we don't add an 'S' in third person). See the following structure:

Subject + Modal Verb + Verb (base form of the infinitive)

• I can speak English (NOT: I can to speak English)
• He can speak Spanish (NOT: He can speaks Spanish)
• She can speak Spanish (NOT: She cans speak Spanish)

Modal Verbs in Negative Sentences

Subject + Modal Verb + not + Verb (base form of the infinitive)

• You must not walk on the grass. (= You mustn't walk on the grass.)
• He cannot speak Arabic. (= He can't speak Arabic.)
• We should not be late. (= We shouldn't be late.)

As you can see in the examples above, contractions of the Modal verb + not are normally possible.

The negative of can is cannot ('not' is joined to 'can') and the contraction is can't

Modal Verbs in Questions

Modal Verb + Subject + Verb (base form of the infinitive)

• May I help you?
• Can I have another piece of cake please?
• Would you like to come with us?

Can - Could

Both Can and Could are Modal Verbs. In general Could is considered more polite (or formal) that Can.

CAN

The three main uses of Can are: 1) ability 2) possibility and 3) permission. However there are some other used of Canas we will see below.

1. To express ability

Can means to be (physically) able to do something OR to know how to do something.

• Birds can fly.
• Elephants can't fly.
• I can speak two languages.

2. To express a possibility (in general)

This refers to a theoretical possibility.

Note: we don't use can to talk about future possibilities. For this you would use may or might.

• It can get cold there at night so take a jacket.
• I know you can win the competition.
• Well, I think your car can be repaired, but it's not going to be cheap.

3. To offer to do something for others

Can is used when you offer to help someone or to do something for them.

• You don't need to walk home. I can take you there if you like.
• Can I carry your bags for you?

4. To ask for or give permission / To request something

Can is used to ask for / request permission or to give permission.

Note: Can't is used to refuse permission.

• You can use my umbrella, I don't need it right now.
• Can I sit in that chair please?
• Mary, you can play outside if you like.
• Can I ask you a question?
• You can't go to the park. It will still be wet from the rain last night.
• We can't leave the room until the assignment is completed.

5. Can't: Something that is forbidden or not allowed

• We cannot park the car next to this fire hydrant.
• You can drive as fast as you want on the German motorways.
• You can't smoke in the restaurant.
• You cannot drive a car without a license.

6. Can't: when you are sure that something isn't true or something is surprising

• It can't be dark outside! It's only 4.30pm!
• They can't have landed on the moon, I'm sure it's a hoax.

For more examples, including how to make questions, see our grammar notes about Can - Cannot. You might also want to see our Can - Can't - Cannot Game

COULD

Could is similar to Can and often replaces Can in the past tense (though not always)

1. To express ability in the past

• I could ride a horse when I was younger but now I can't.
• She could juggle eight balls when she was only 10 years old.
• He could read when he was three years old.

2. Polite word used to ask for permission or to request something (in the present)

• Could I please use your bathroom?
• Could we move on to the next topic now please?
• Could you pass me the salt please?
• I'm busy right now. Could you call back later?

3. General permission in the past

• In high school, we couldn't leave the classroom without a pass.
• He couldn't go to the concert because his mother wouldn't let him.

4. A suggestion when asked what to do (choices and opportunities)

• He could try and fix it himself.
• We could go to the movies if you are interested.

5. Couldn't: Sure that something is untrue

Just like can't, you can use couldn't when you are sure that something isn't true or real.

• That couldn't be my cat meowing outside, it was hit by a car last week.
• He couldn't have painted that. He has no artistic ability at all.

6. Could + have + past participle: To express a possibility in the past

To express that something was possible but did not happen.

• We were lucky because it could have rained but it didn't.
• Why did you do that? You could have broken your leg.

7. Could + have + past participle: Unrealised past ability

This is used to say that someone was able to do something, but they did not try to do it. Sometimes this is a form of criticism.

• She could have married anyone she wanted to.
• Why did you sit there doing nothing? You could have helped me.

8. Could: A conditional form of Can

Would + Can = Could. Note: Would be able to can replace could in the following examples.

• If we had some oranges I could make you some fresh juice.
• I could write the letter if you told me what to include.

Can vs Could Summary Chart

May - Might

May and Might

1. To express (future) possibility

There is a chance that something is true or that there is a possibility of something happening.

Note: Might is used more frequently than May in spoken English.

• It might rain later (= it is possible that it will rain)
• I might go to the movies tonight. (Though I'm not sure)
• I wouldn't talk to Tim right now. He may still be angry after his team lost.
• He's very good, in fact, I think he may win the competition.
• She might be late because of the public transport strike.

2. To give permission

• You may leave the table once you have finished your meal.
• You may take only one brochure.
• If you have finished the exam, you may leave the room.

May not can be used to NOT give permission or to prohibit someone from doing something.

• You may not park your car in front of the gate.
• You may not take more than one brochure.

3. To ask for permission

Note: Can is used more frequently than May in spoken English though May sounds more polite.

• May I sit next to you?
• May I borrow your pen?
• May I use your bathroom please?

Note: Might could also be used to request permission but it sounds very old and is not common.

4. May: to talk about typical occurrences

May is used in academic (or scientific) language to refer to things that typically happen in certain situations.

• Drivers may feel tired if they do not take a break every 2 hours.
• Adults may find it difficult to sleep if they use technology before going to bed.
• These tablets may produce serious side effects if not taken in the correct dosage.

5. Speculate about past actions (May + have + past participle)

• She is late. I think she may have missed her plane.
• It may have already been broken before you bought it.
• What was that noise? It may have been a dog outside our window.

6. To express wishes

• May you both live a long and happy life together.
• May the New Year bring you love and happiness.
• May all your wishes come true.
• May the odds be ever in your favor.
• May the Force be with you. :)

Must

1. To express obligation or duty

This also refers to laws and regulations.

• I must memorize all of these rules about modal verbs.
• People must remain seated until the show is over.
• You must wear a seatbelt at all times.

2. To emphasize the necessity of something

• Humans must have drinking water at least every two days.
• You must give up smoking, it's bad for you.
• We must have a special permit to camp in the national park.
• You must study the last two chapters before the test.
• Plants must have light and water to grow.
• You must drive carefully.

3. Deduction - Sure that something is true (Certainty)

We use this when we don't know but we are certain that it is true (based on evidence).

• Look at all of that snow. It must be really cold outside.
• The ground was wet this morning. It must have rained last night.
• Dinosaurs were very big, they must have eaten a lot.
• It's five in the morning and you still haven't gone to bed? You must be tired!
• Jack must be home. I heard a noise coming from his room.

4. Expresses positive logical assumptions (Must + have + past participle)

• That must have been my mother calling me last night, nobody else has my number.
• He must have won the lottery with the new house and car he has just bought.
• She must have been at home - her car was there.

5. A strong recommendation

Something that is highly recommended (stronger than using should)

• We really must get together for dinner sometime.
• You must see the new Peter Jackson movie, it's fantastic.
• The ice cream here is delicious. You must try some.

Mustn't

The negative is Mustn't which refers to prohibition (negative obligation)

Mustn't = Must not

• You mustn't use your smartphone while you are driving.
• You mustn't get on the subway if you haven't paid for the ride.
• You must not open the gift until it is your birthday.
• We must not tell anyone.

Must vs. Have to

Must can be replaced by Have to with little difference in meaning:

• You have to study. (= you must study)
• He has to finish the report by Friday. (= He must finish the report by Friday)
• They have to resit the test. (= They must resit the test)

Have to is a more informal while Must is mostly used in written orders or instructions.

Also, Must expresses obligation imposed by the speaker while Have to expresses external obligation.

• Teacher: You must complete this essay by Friday
• Student: We have to complete this essay by Friday.

When we are mentioning someone else's obligations, we use Have to.

• John has to quit smoking.

For questions it is more common to use Have to instead of Must (which sounds very formal):

• When do you have to pay finish the report?
• Does he have to take a blood test?

The past tense of Must is Had to:

• I had to pay my speeding ticket yesterday.

Mustn't vs. Don't have to

Be careful with the negative of Must and Have to where they DO have a different meaning. Mustn't is a negative obligation (= it is important that you do NOT do something) while Don't have to is an absence of obligation.

Mustn't = it is prohibited; it is not allowed

Don't have to = no obligation; you are not required to do something, especially if you don't want to.

• You must not drink that. (= it is forbidden to drink that; it is not allowed)
• You don't have to drink that. (= you don't need to drink that but you can if you want)
• You mustn't tell John (= Do not tell John)
• You don't have to tell John (= you can tell John if you want to but it is not necessary)

SHOULD

1. To give advice, a recommendation or a suggestion

This is to say that it is the right thing to do or the correct thing.

• Does your tooth still hurt? You should make an appointment with the dentist.
• I think you should study for the test so that you don't fail.
• Your hair is too long. You should get a haircut.
• You really should go to the new restaurant on Main Street.

2. Expresses that a situation is likely in the present

• Mary should be at home by now. Give her a call.
• He should have the letter by now. I sent it a couple of weeks ago.

3. Expresses that a situation is likely in the future (prediction)

• They should win the game because they are a much better team.
• I posted the cheque yesterday so it should arrive this week.
• It should be fine tomorrow.

4. Expresses an obligation that is not as strong as Must.

Sometimes Should is used instead of Must to make rules, orders or instructions sound more polite. This may appear more frequently on formal notices or on information sheets.

• On hearing the fire alarm, hotel guests should leave their room immediately.
• Passengers should check in at least 2 hours before departure time.
• You should never lie to your doctor.
• You should pay more attention in class.
• You should be at work before 9.

All of the above example sentences can have must instead of should making the obligation stronger and less polite.

5. Was expected in the past but didn't happen (should + have + past participle)

This expresses the idea that the subject did not fulfill their obligation in the past or did not act responsibly.

• You should have given your boss the report yesterday when he asked for it.
• I should have studied more but I was too tired.

6. Not fulfilling an obligation (should + be + verb-ing)

This expresses the idea that the subject is not fulfilling their obligation or is not acting sensibly.

• You should be wearing your seatbelt. (The person isn't wearing one right now)
• We should be studying for the test. (We are not studying right now and we should)

7. Sometimes should is replaced by ought to without a change in meaning. Note that ought to sounds more formal and is used less frequently.

• You ought to study more. (= you should study more)
• He ought to go home. (= He should go home)
• They ought to stop doing that. (= They should stop doing that)

Shouldn't

We use shouldn't to advise not to do something, usually because it is bad or wrong to do.

• You shouldn't throw your litter onto the street.
• We shouldn't leave without saying goodbye.
• He shouldn't play with those wires if he doesn't know what he is doing.
• Are you tired? You shouldn't work so much.
• You shouldn't talk like that to your grandmother.

Should Summary Chart

WOULD

1. Used as a polite invitation or to offer

• Would you like to go to the movies with me tonight?
• Would you like some more tea?
• I would be happy to help you with preparation for your exam.

When someone asks a question to invite you or offer you something using Would, the response can be: Yes, I would OR No, I wouldn't.

• Would you like to have a coffee with me? Yes, I would.

2. Describe a prediction (hypothetical situations)

• It would be nice to have a barbecue.
• Nobody would believe me if I told them I had seen a UFO.

3. To not sound impolite when disagreeing with someone

• It would like to point out that you need to review those numbers.
• I wouldn't agree with that.

4. To describe past habits

• Before internet people would send letters to each other.
• When I was at school I would get up before everyone else in our house.

(This is similar to using Used to)

5. Future in the past

We use would when we are talking about the past but we want to talk about something which was in the future at that time (in the past).

• When I was in Paris last year I would spend hours sitting at coffee shops writing ideas for my novel.
• She promised she would send a postcard from Peru.
• I told you he would help us.

6. Wouldn't: To describe a past unwillingness (refusal)

• He said he wouldn't help us.
• My son wouldn't eat his food.