Answer:
A modal is a type of auxiliary (helping) verb that is used to express: ability, possibility, permission or obligation. Modal phrases (or semi-modals) are used to express the same things as modals, but are a combination of auxiliary verbs and the preposition to.
Step-by-step explanation:
Modal verbs show possibility, intent, ability, or necessity. Because they're a type of auxiliary verb (helper verb), they're used together with the main verb of the sentence. Common examples include can, should, and must.