Modal Auxiliaries

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Modal Auxiliaries

Modal verbs are a kind of auxiliary verb. They facilitate the main verb for suggesting potential, expectation, permission, ability, possibility, and obligation.

When used with the main verb, modal verbs do not end with -s for the third-person singular.  Modal auxiliary verbs never change form, but they have a different form for past tense.

The modal auxiliaries include:

Present Tense Past Tense



Must (have to)


Should (ought to) (had better)

Would (used to)


(Had to)


Should (ought to)

NB: The words in parentheses ( ) are semi-modals. They have the same meaning, but they are different grammatically.

Will – Would

Will indicates a ‘willingness’ to do something in the future. The negative form of willwill not (won’t) indicates an ‘unwillingness’ (refusal, reluctance) to do something.


  • I will give you another opportunity.
  • I will play tomorrow.
  • They will arrive at 10 AM.
  • She won’t come today.

Would indicates general or repeated willingness in the past. It also indicates preference in the present.  


  • If you did not leave, I would still be taking care of you.
  • Whenever I had to go there, they would throw a party.
  • We thought that people would buy this book.
  • If I were you, I would not do it.
  • I would like to make a toast.


Used to sometimes replaces would but sometimes it would be grammatically incorrect if we use used to in place of would.  


  • When I was in school, I used to make sketches.
  • He often used to cry at night without reason.
  • I used to take a break at this time of the year.

Can – Could – May – Might

These modals express possibility and ability.

Can indicates ability. Could indicates ability with an option.


  • I can do it. (The subject ‘I’ is sure about his/her ability)
  • I could do it. (The subject ‘I’ is not sure about his/her ability)
  • They cannot do it. (present)
  • They could not do it. (past)

Can & could also indicate possibility.


  • The temperature can rise this month.
  • They can’t go too far by now.
  • It could rain later.

May and might both indicate possibility but might can suggest that there is less possibility than may.  


  • It may rain later.
  • It might rain later.
  • They may come back.
  • They might come back.


Must indicates necessity.


  • I must leave now.
  • He must study hard.
  • Alex must go home by 6.00 pm.

Have to has the similar meaning to must but implies less urgency.  


  • I have to leave now.
  • He has to study hard.
  • Alex has to go by 6.00 pm.
  • I had to leave then. (past)
  • He had to study hard to pass the exam. (past)


Should indicates obligation and probability.


  • You should come home early.
  • You should not smoke at all.
  • I should visit my parents more often.
  • There should be an extra key for the lock in the drawer. (probability)
  • He should have reached by now. (probability)
  • I should have done that. (obligation in the past)

Ought to and had better sometimes replaces should.


  • You ought to come home early.
  • We ought to have taken a taxi. (Past)
  • We had better leave. (Had better is generally used in spoken English.)
  • I think parents ought to give children more freedom. (Had better won’t be appropriate here.


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