What are modal auxiliaries?

1. Auxiliaries, Modals and Main verbs

be, have and do can be auxiliaries and main verbs. They have grammatical functions and are used for forming tenses, questions, the passive, etc.

Modals are can, could, may, might, must, ought to, shall, should, will, would and need (need can also be a main verb).


  • We can play football.
  • We could play football.
  • We may play football.
  • We might play football.
  • We must play football.
  • We mustn't play football.
  • We needn't play football.
  • We ought to play football.
  • We shall play football.
  • We should play football.
  • We will play football.
  • We would play football.

2. What to keep in mind when using modals

Explanation Sample sentences
Do not use modals for things which happen definitely. The sun rises in the east. - A modal can't be used in this sentence.
They have no -s in the 3rd person singular. He can play football.
Questions are formed without do/does/did. Can he speak Spanish?
It follows a main verb in its infinitive. They must read the book.
There are no past forms (except could and would). He was allowed to watch the film.
When you use the past participle you tell about things which did not happen in the past. You should have told me.

3. Long and contracted forms of modals

Affirmative Negative
Long forms Contracted forms Long forms Contracted forms
can -- cannot can't
could -- could not couldn't
may -- may not --
might -- might not --
ought to -- ought not to oughtn't to
need -- need not needn't
shall 'll shall not shan't
should 'd should not shouldn't
will 'll will not won't
would 'd would not wouldn't