Auxiliary & Modal Verbs

Auxiliary verbs are a closed group of words. There are three types of auxiliary verbs: 

What are auxiliary verbs? 

There are 24 verbs in English that help the main verbs to form tense, voice, negative, interrogative, etc. They are: am, is, are, was, were, have, has, had, do, does, did, shall, should, will, would, can, could, may, might, must, dare, need, used to, and ought to.
Types of Auxiliary Verbs
There are three types of auxiliary verbs: primary auxiliary, modal, and semi-modal verbs. 
Primary Auxiliary
The primary auxiliaries are to be, to have, and to do verbs.