Modal verbs in English: what each one means and how to use it in speech

What modal verbs are and the four grammar rules

BBC Bitesize describes modal verbs as verbs that support other verbs in a sentence to indicate possibility or necessity. It lists them: must, shall, will, should, would, can, could, may and might, and adds that modal verbs are easy to spot because there are so few of them.

The grammar is the same for all of them. Cambridge Dictionary says that modal verbs are placed first in the verb phrase (after the subject) and are followed by a verb in the base form, and that they do not change form for tense or person. The same page notes that modal verbs cannot be used with another modal verb.

LSI's guide to may and might gives the same pattern: modal verbs do not take any endings like -s, -ed or -ing, are followed by the base form of another verb (may do, might be), and make questions by inverting the subject and the modal verb (may I…).

So there are four rules:

1. Modal + base verb: She can swim. (not She can swims or She can to swim)
2. No endings: He must go. (not He musts go)
3. Questions by inversion: Can you help me? (not Do you can help me?)
4. Negative with not: You should not worry. (not You don't should worry.)

A fifth, smaller point from Cambridge: modal verbs can be used alone when the main verb is clearly understood, as in Can you swim? Yes, I can.

Modal verbs by function: the quick table

Do not try to learn each modal in isolation. Learn them by what you want to do with them.

Most modals have more than one meaning. Could can mean past ability (I could run fast as a child), a polite request (Could you help me?) or a possibility (It could be true). The context tells you which one.

The sections below take these functions one at a time.

Ability: can and could

Can shows present ability. Could shows past ability, or polite possibility.

• I can drive a car. (present ability)
• She can't speak Spanish. (present, negative)
• I could swim when I was five. (general past ability)
• Can you swim? Yes, I can. (short answer)

For one specific achievement in the past, use was able to, not could: I was able to finish the report yesterday. Could is for general ability over time.

Be able to replaces can when you need another form: I will be able to help you tomorrow. (Not will can, because a modal cannot follow another modal.)

Be careful with can and can't in speech. In normal sentences, can is weak ("kn"): I can do it sounds like "I kn do it", and can't is strong and long. The difference is in the vowel and in the stress, because the final t is often hard to hear. Listen for the stress to tell them apart, and say can't with a clear, full vowel when you mean no.

Permission and requests: can, could, may, would

Permission asks whether you are allowed to do something. Requests ask someone else to do something. The modals differ in politeness.

Permission (you want to do something)

• Can I use your phone? (informal)
• Could I use your phone? (more polite)
• May I use your phone? (formal)

Requests (you want someone else to do something)

• Can you help me? (informal)
• Could you help me, please? (polite, most useful)
• Would you help me, please? (polite)
• Would you mind helping me? (very polite)

Offers

• Can I help you? / Shall I open the window? / I'll carry that for you.

A useful rule: the further the modal is from can, the more polite it sounds. For most everyday requests, Could you…? is the best choice: it is polite but not stiff.

For the opposite situation, saying no politely, see our guide to how to say no politely, which uses several of these modals (I'm afraid I can't, I'd rather not).

Possibility: may, might, could

To say that something is possible but not certain, use may, might or could. The differences are small.

• It may rain this afternoon. (a real possibility)
• It might rain this afternoon. (a possibility, a little less sure)
• It could rain this afternoon. (it is possible)

In everyday speech, might and may are almost the same. Might is used a little more when you are less sure, and it is the usual form in the past: He might have missed the train.

The negative forms follow Cambridge's patterns. LSI notes that we never use a contraction for may not (you might find mayn't in a dictionary, but it is not used), and that the negative form of might is might not plus the base form. The contracted form mightn't is not used in American English, but it is used in British English.

So say:

• She may not come. (not mayn't)
• She might not come. (or British: mightn't)

Past possibility uses have + past participle: He may have forgotten. She might have lost her keys. It could have been worse.

Must and can't show strong certainty (a deduction): She must be at home. The lights are on. He can't be at work; it's Sunday.

Advice and obligation: should, must, have to, ought to

Advice says what is a good idea. Obligation says what is necessary.

Notice the important difference between must not and don't have to:

• You must not tell anyone. (it is forbidden)
• You don't have to tell anyone. (it is not necessary, but you can)

Should is the safest way to give advice, because it is polite and clear. If you want to be even softer, say You might want to… or Have you thought about…?

Have to is not a modal verb in the strict sense, because it takes -s and do: She has to go. Do you have to leave? But it is used like a modal, so learn it with them.

Will, would, shall and the past

Will shows predictions, promises and quick decisions.

• It will be sunny tomorrow. (prediction)
• I will call you tonight. (promise)
• I'll take the red one. (decision at the moment of speaking)

Would has several uses.

• Polite request: Would you open the window, please?
• Past habit: When I was a child, we would visit my grandparents every summer.
• Imaginary situation: If I had more time, I would learn Italian. (second conditional)
• Past in reported speech: She said she would call.

Shall is mainly used in British English, for offers and suggestions: Shall I help you? Shall we go? In American English, people usually say Should I…? or Do you want me to…?

Past forms: modal verbs do not change for the past, so you build the past with have + past participle.

• I should have called. (but I didn't)
• She could have won. (but she didn't)
• They must have left. (I conclude they left)
• He might have forgotten.

Past modals are the backbone of regret, criticism and deduction, and they are very common in conversation.

How modal verbs sound in speech

In fast, natural English, modal verbs are weak and short. Learners who say each one clearly sound slow and robotic, and may find fast native speech hard to follow.

The important idea is that the word have in should have is weak and sounds like -a or -uv. In writing, always write should have, never should of. Should of is a spelling mistake that comes from the sound.

Contractions are normal in speech: I'll, you'd, we'd, shouldn't, can't, won't. For how they sound, see our guide to contractions in English. For the weak vowel in these small words, see the schwa sound.

Practise with a short sentence, said fast: "I should've called you." (shud-uv). Compare with the careful version: "I should have called you."

Common mistakes with modal verbs

• Wrong: She can to swim. Right: She can swim.
• Wrong: He musts go. Right: He must go.
• Wrong: Do you can help me? Right: Can you help me?
• Wrong: I will can come. Right: I will be able to come.
• Wrong: You should to see a doctor. Right: You should see a doctor.
• Wrong: He might to be late. Right: He might be late.
• Wrong: I should of called. Right: I should have called.
• Wrong: You don't must go. Right: You must not go. (or: You don't have to go.)

Also remember Cambridge's rule that modal verbs cannot be used with another modal verb. You cannot say You must should go. Choose one: You must go or You should go.

If you want regular practice, short conversations are the best way to learn modals, because you hear them in context. See our collection of short English conversations for models you can say aloud.

Quick quiz: choose the best modal

Choose the best modal verb. Answers follow.

1. ___ I borrow your pen? (polite permission)
2. You ___ see a doctor. (advice)
3. She ___ speak French when she was a child. (past ability)
4. It ___ rain later. (possibility)
5. Visitors ___ not touch the paintings. (prohibition)
6. ___ you open the window, please? (polite request)
7. I ___ have called you. I forgot. (regret)
8. We ___ wear a uniform at work. (rule)

Answers: 1. May / Could. 2. should. 3. could. 4. might / may. 5. must. 6. Could / Would. 7. should. 8. have to / must.

Read each sentence aloud, using the weak forms of the modal verbs. Then write four sentences of your own about your day, using a different modal in each. For a daily routine that builds this skill, see our English speaking practice guide.