am, is, are, was, were, do, does, did, have, has, had are called Primary Auxiliaries.
Will, shall, would, should, can, could, may, might, ought to, must, need are called Modal Auxiliaries.
The Primary Auxiliaries can be used as helping verbs as well as principal verbs.
The Modal Auxiliaries are always used as helping verbs. In other words they cannot be used as Principal verbs.
I am a software professional.
I am working for Wipro.
In the above first sentence ‘am’ was used as a principal verb and in the second it was used as a helping verb.
He is a doctor.
He is performing a surgery at the movement.
We are students of Hansraj College.
We are participating in a football tournament here.
Kalidasa was a great poet.
Gopal was riding a bi-cycle when he was hit by a scooter.
They were my classmates in Dehradun.
They were going to Goa when their train met with an accident.
I have many grammar books at home.
I have read all of them.
He has a laptop with him.
He has put it in his briefcase.
I had a beautiful pen.
I had bought it in 2004.
They do their work sincerely.
They do not go home before 8 pm.
He does his work efficiently.
He does not waste even a single minute.
She did her job.
Did she come to office yesterday?
Modal Auxiliaries can only be used as a helping verb.
Will – It is used to express intention. It is normally used in future tense.
We will go to Jaisalmer next week.
They will visit our place in February.
Will they accompany you for lunch?
Would – It is the past form of will.
He would complete his work by this time tomorrow.
She would be going for her dance classes from next week.
Would you like to have a glass of water?
Shall I take leave tomorrow?
Shall we go on a picnic next week?
Shall we have coffee in CP?
You should pay attention in the class.
Should I accompany her to her house?
You should drink two glasses of water daily in the morning.
May – It is used to indicate possibility.
I may come to your house tomorrow.
It may rain in the evening.
Government may hike the price of petrol and diesel.
May I borrow your book for a couple of days?
Might – It is the past form of may and is used to express less certain situations.
I might take a leave tomorrow.
Dad might come to office the day after tomorrow.
Mid term elections might be announced in mid March.
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