
Modal Auxiliary Verbs are a special class of auxiliary verbs. Like other auxiliaries, modals help another verb in the sentence. But this special class of verbs follow a different sentence structure, and have their own set of rules.
Modal Auxiliary Verb Sentence Structure:

Learn more about Modals:
Silly Comparisons Game
Will
Would you rather…?
Would or Used to
Would like, like, want
Can
Could
Must and Have to
Modals in the 1st, 2nd and 3rd Conditional
Practice mixed modals with the Around Town game