Conjugation and verb forms of modal auxiliary verbs in the past simple

(Formation of the past simple of the modal verbs: can, must, may, used to, ought to)

Table of contents – past simple of modal auxiliary verbs

On this page you will find the following:

  1. Formation of modal auxiliary verbs in the past simple
  2. Verb forms of ‘can, ought to, must, used to, may’
  3. Further explanations and exercises

Formation of the past simple of modal auxiliary verbs (can, must, may, used to, ought to)

The following modal auxiliary verbs have unique forms in the past simple, which may sometimes differ in meaning. Compare the following example sentences as well as the use in the table below:

  • Examples of the auxiliary verbs ‘can, must, used to, ought to’ in the past tense as they may occur in a sentence:
    • “When Jim was a child, he could speak Italian fluently.”
    • “The policeman said I had to get out of the car.”
      • Be careful when using ‘must’ – it becomes ‘had to’.
  • Information: Refer to present simple of modal verbs for present tense forms.

Verb forms of ‘can, ought to, must, used to, may’ in the past simple

The column ‘past simple’ also lists possible forms for substitution. These substitute forms may have slight differences to the standard forms:

Modal verb Past simple & possible substitute form Example Comment

can

could
or
was/were able to
  • “He could easily win every race when he was young.”
  • “I was able to get in without a ticket.”

There is a small difference in meaning (detailed usage: can / be able to).

must

had to
or
had got to*
  • “I had to pay the bill.”
  • “She received an emergency call and had got to go early.”

–

may

was/were allowed to
or
might
  • “We were allowed to pass.”
  • “She said she might move to Australia.”

‘may’ can also become ‘might’ for grammatical reasons (see difference ‘may/might’).

used to (for the usage in detail, see ‘used to’)

used to
  • “I used to go jogging every day.”
  • “He didn’t use to go out.”
  • “We used not to go to parties.”

No present tense possible.

ought to

ought to
  • “We ought to get home early.”
  • “This ought to be enough.”
  • “They ought to study the language.”

Only occasionally used; in most cases, ‘should’ is preferred instead.

*British English

Further explanations related to the ‘Formation of modal verbs in the past simple’

The following explanations relate to the topic ‘Conjugation and verb forms of the past simple of ‘can, used to, ought to, must, may’’ and could also be interesting:

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