Modal verbs (modal auxiliary verbs)


Modal verbs

modal_verbsModal verbs (also called modal auxiliary verbs, or modals) are used with the infinitive form of the main verb (minus -to) to add additional layers of meaning to a sentence.

Modal verbs are also called modal auxiliary verbs, or modals.

Here are some examples:

  • I can play the piano.
  • She may know his name.
  • I must try harder.

Examples of modal verbs

The following are all modal verbs:

  • can
  • could
  • may
  • might
  • must
  • shall
  • should
  • will
  • would
  • would rather
  • ought to

Modal verbs can refer to:

  • ability – I can drive a car.
  • probability – I might go to the party later.
  • deduction – That must be the man she was talking about, he fits the description she gave me.
  • obligation – I have to go to the meeting or my boss will be annoyed.
  • necessity – I must leave early today.
  • prohibition – You cannot smoke in here.
  • permission – May I leave early?
  • instructions and requests – Could you help me?
  • suggestions – We could go to the cinema to see that new movie this evening.
  • advice – You ought to notify them straight away and sort out the problem.
  • recommendation – You should watch the film – it’s fantastic!
  • preference – I would rather finish this before we go.
  • promise – I will definitely call you first thing in the morning. (see future simple lesson)
  • prediction – You will love it there! (see future simple lesson)
can (positive), can’t (negative), could (past positive) couldn’t (past negative)
Example sentences using modal verbs for ability
  • I can sing, but I can’t dance.
  • I could swim when I was six, but I couldn’t ride a horse.

You can use different modal verbs to talk about probability (deduction). The difference in meaning is how certain you are about what you are talking about.

  • will (very certain)
  • must (expressing opinion you are quite sure about)
  • should (expressing opinion you are quite sure about)
  • might (possible)
  • could (possible)
  • may (possible)
  • can’t (expressing opinion you are quite sure about)
  • won’t (very certain)
Example sentences using modal verbs for probability (deduction)
  • She will be at work now, she never finishes before 6pm.
  • He must be stuck in traffic, the road we so busy when I was coming home.
  • I should finish this soon, I don’t have too much left to do.
  • He might call later if he remembers your birthday.
  • He could be out with his friends, I’m not sure where he is.
  • She may come later, I’m not sure what her plans are.
  • It can’t be John over there. It looks like him, but I’m sure John is overseas at the moment.
  • I won’t finish the report today, there have been too many interruptions and I have to leave soon.

Modal verbs – obligation (necessity)

You can use the modal verbs ‘have to‘, ‘must‘ ‘ought to‘, ‘should‘ to talk about obligation.


Modal verbs ‘have to‘ and ‘must‘ talk about necessity / strong obligation.

Modal verbs ‘ought to‘ and ‘should‘ talk about lower level of obligation.

You use ‘have to‘ when the obligation comes from someone else – e.g. it’s a law or a rule.

  • In most countries you have to wear a seatbelt when travelling in a car.


  • Drivers ought to / should drive slower in wet weather.

Obligation is not as strong as the legal requirements is to drive to the speed limit but driving carefully is still a moral obligation for motorists on the road.

Must‘ is used when the obligation comes from the person speaking.

  • I must stop smoking.

You can use ‘don’t have to‘ when there is no obligation.

  • College students don’t have to wear a uniform. (there is no rule for them to wear a uniform).

BE CAREFUL – you cannot use must not to show no obligation. This has a different meaning. It means ‘cannot, not allowed to, no permission to’.

For example:

‘You mustn’t interrupt when someone is talking dear.’ the mother told her son.  (the child is not allowed to interrupt other people).

To talk about obligation in the past, use ‘had to‘.

  • My grandfather had to walk four miles to school everyday when he was a child.

Modal verbs – prohibition

Modal verbs ‘must not‘ (mustn’t) and ‘cannot‘ (can’t) are used to talk about prohibition. Prohibition means something cannot happen, it is not allowed, there is no permission.

Must not‘ – see example in the previous section. Mustn’t is more commonly used when the prohibition comes from the speaker.

Another example is:

  • “You mustn’t sit on the desks in my classroom.” said the teacher.

Cannot‘ – more commonly used when the prohibition comes from someone else, e.g. a rule or a law.


  • Employees cannot use Facebook during office hours.

To talk about prohibition in the past, use ‘could not‘.

  • Women could not vote in the USA until 1920.

Modal verbs – permission

Modal verbs ‘can‘, ‘may‘ and ‘could‘ are used to ask someone for, or to give permission (you want to be allowed to do something, or you are allowing someone to do something).

  • Can I go home now?
  • You can borrow my jacket if you’re cold.
  • Could I ask you a question?

Note: ‘could‘ can be used to ask for permission. It is more formal / more polite than ‘can‘.

  • May I use your telephone?
  • You may now kiss the bride.

Note: ‘may‘ can be used to ask for and to give permission. It is more formal / more polite than ‘can‘.


Modal verbs – instructions and requests

Modal verbs ‘can‘, ‘will‘, ‘could‘ and ‘would‘ are used to ask someone, or tell someone to do something.

  • Can you make me a coffee, please?
  • Will you call me a taxi, please?
  • Could you take this luggage to my room, please?
  • Would you ask him a question for me?

Note: ‘would‘ and ‘could‘ are more polite than ‘can‘ or ‘will‘. When asking or instructing someone to do something, you should also say ‘please’.

Modal verbs ‘should‘ and ‘ought to‘ are used to give suggestions, advice and recommendations.

  • We should go out for dinner next week. (suggestion)
  • We ought to go out for dinner next week. (suggestion)
  • You should inform the boss straight away. (advice)
  • You ought to inform the boss straight away. (advice)
  • You should stay at the Apollo Hotel, it’s amazing! (recommendation)
  • You ought to stay at the Apollo Hotel, it’s amazing! (recommendation)

Could‘ is also used to make suggestions.

  • We could meet up at 8pm, does that suit you? (suggestion)

We also use modal verbs ‘will‘ and ‘would‘ in conditional sentences to give advice.

A commonly used second conditional phrase is: “If I were you, I would……”

  • If I were you, I would tell the boss straight away. (advice)


  • The boss will help you, if you tell him. (first conditional)
  • The boss would help you, if you told him. (second conditional)

You can also use ‘must‘ to give advice. ‘Must‘ is stronger than ‘should‘ or ‘ought to‘.

A speaker who uses ‘must‘ thinks what they are suggesting, advising or recommending is so important (it is like an obligation) for the person to do that.

For example:

  • You must get those tyres on your car changed. They are so dangerous!


Would rather‘ is used to talk about preference.

  • I would rather work late tonight. I can have tomorrow morning off then.

If you are comparing options, you use ‘would rather…….. than….’

  • I would rather work late tonight, than have to work tomorrow morning.

Use would rather not (negative form) to talk about something you don’t want to do.

  • I would rather not work tomorrow morning.
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