The past tense modals look quite different from the root forms . An end run might just work. To make commands and requests more polite. To refer to events in the past. No one thought he could escape.
Modals are sometimes confused with auxiliary verbs.
This confusion is understandable since modals and auxiliaries have many syntactic characteristics in common. Look at the verb which follows them. - after modals the verb is in root form . We could play gin rummy. We are playing gin rummy 2. Look at the meaning.