4.102 form of following verb

Modals are followed by the base form of a verb.

• I must leave fairly soon.
• I think it will be rather nice.
• The rich ought to pay the tuition fees of their sons and daughters.

Note that 'ought' is sometimes regarded as a modal, rather than 'ought to'. 'Ought' is then said to be followed by a 'to'-infinitive.

4.103

Sometimes a modal is followed by the base form of one of the auxiliary verbs 'have' or 'be', followed by a participle.

When a modal is followed by 'be' and a present participle, this indicates that you are talking about the present or the future.

• People may be watching.
• You ought to be doing this.
• The play will be starting soon.

When a modal is followed by 'have' and a past participle, this indicates that you are talking about the past.

• You must have heard of him.
• She may have gone already.
• I ought to have sent the money.

In passive structures, a modal is followed by 'be' or 'have been' and a past participle.

• The name of the winner will be announced.
• They ought to be treated fairly.
• Such charges may have been justified.

A modal is never followed by the auxiliary verb 'do', or by another modal.