Grammar Handbook: Auxiliary Verbs

Auxiliary or helping verbs are verbs that are used to help form verb phrases but cannot do so independently. There are four basic auxiliary verb groups:

To Be
To Have
Modal Auxiliaries
To Do

:: To Be
This auxiliary verb is used in the progressive tenses and passive voice:

Progressive Tense:
You are kicking.
You were kicking.
You have been kicking.

Passive Voice:
You are kicked.
You were kicked.
You have been kicked.

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:: To Have
This verb is used as an auxiliary in the perfect tense:

I have finished my paper.
I had finished my paper.
I have been finished with my paper.

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:: Modal Auxiliaries
These auxiliaries affect the mood of the verb; that is, they determine whether a verb is a fact, desire, possiblity, or command. They are most commonly used to represent degrees of freedom or severity.

Most common modal auxiliaries:
will, shall, can, may, need (to), dare, would, should, could, might, must, ought (to)

Ability: I can run.
Necessity: I must run.
Obligation: I ought to run.
Permission: I may run.

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:: To Do
This verb is used when the main verb of the sentence requires aid of an auxiliary, but there is no other helping verb that will fit. It is often used in questions, negative or emphatic statements:

Does he drive?
He drives, doesn't he?
Despite his flat tire he does drive.

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