Auxiliary Verbs
TO BE
In Progressive (Continuous) tenses
We are watching TV in our room right now. (present progressive)
Sally was shopping when I saw her. (past progressive)
They have been running for an hour. (present perfect progressive)
We had been sleeping for an hour when the fire alarm rang. (past perfect progressive)
Note: we always use the "-ing" form of the main verb following the auxiliary verb.
In Passive Voice
The window is broken.
The bridge was built.
The new program has been declared.
It should be renovated.
Your assignment must be finished by tomorrow.
Have
In Compound Tenses
They have cleared all the evidence.
Nobody has seen anything.
She has been singing.
We had arranged everything.
Nothing has been done about the incident.
DO
In Negatives
John didn’t participate our club.
I don’t like horror films.
In Questions
In emphasis
Does your brother know Spanish?
Did you attend the course yesterday?
I do want to marry you.
Note: these three auxiliary verbs (be, do and have) can also be used as full verbs, so pay attention to the words coming after them to distinguish between the two uses.
I am so exhausted today.
"To be" is the main verb of the sentence here as it isn't followed by a full verb.
I have a car and it is so expensive.
Both the verb “have” (indicates possession) and “to be” are full verbs in this sentence.
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Can you do me a favor please?
I am doing my best to pass my class.
The verb "do" is the main verb in this sentence; however, "to be" is an auxiliary verb as it is followed by the main verb (doing).
WILL
Can only be used as an auxiliary verb
I will help you with the chores.
They won’t come today.
Modal Auxiliary Verbs
Can / could / may / might / shall / should / must / ought to / had better
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I cannot talk to you right now.
You had better finish your homework before your father arrives.
We must obey the traffic rules.
I think you should take an aspirin.
He might be in his office.
Could you open the door for me, please?