What is the rule for agreement with modal verbs?

What is the rule for agreement with modal verbs?

The rule for agreement with modal verbs is that they are always followed by the base form of the verb, regardless of the subject. Modal verbs such as can, could, may, might, must, shall, should, will, would, and ought to do not change their form to agree with the subject. For example:

- She can swim.
- They could come.
- He may go.
- We must study.
- You should try.

In all these examples, the modal verbs remain the same regardless of the subject.