Modals are a special type of auxiliary verb.  They always work with another verb, and they behave irregularly to give communicative information about the main function of the verb that follows it. Check out this page for more information!

Modal Rules

There are several special rules we must follow when using modals.  

1. Modals do not agree with the subject, unlike other auxiliary verbs.


I can go later. I am going later.

He can go later. He is going later.

They can go later. They are going later.

2. There is always a verb infinitive (without the “to”) after the modal.


She must have her medicine every day.

You will be sorry for that later.

They might disagree with you.

3. Neither the modal nor its accompanying infinitive form can use the past tense.  Past tense would only be indicated by other parts of the verb phrase.


She might go to the movies. She goes to the movies.

She might have gone to the movies. She went to the movies.

She might have gone to the movies. She has gone to the movies.

She might have been going to the movies. She has been going to the movies.

4. Modals make questions by inversion.


She can go. Can she go?

They might want some. Might they want some?

They will arrive soon. Will they arrive soon?


Uses of Various Modals

Canpresent ability — I can ride a bike.

opportunity — She can help you learn to ride a bike when she is finished.

permissionCan I try to ride the bike now?

possibility & conditional — Anyone can learn to ride if they are not afraid.

requestCan you teach me to ride a bike?

willingness — I can teach you.

Couldpast ability — I could ride a bike when I was younger.

conditional — He could learn to ride, if his father bought him a bike.

possibility — Bill could be a good rider with more practice.

suggestion — Mark could ride his bike to campus to save money.

requestCould I borrow your bike?

Maypolite request or permissionMay I borrow your bike?

possibility — He may be able to assemble your bike tomorrow.

Mightpossibility, but not certainty — I might be able to buy a new bike.

conditional — If the seat is comfortable, it might be a good choice.

suggestion — You might want to lower the seat to reach the pedals.

Muststrong obligation — You must return the bike in good condition.

necessity — I must get to the bike store before closing.

Shallformal invitation & future actionShall we ride bikes tomorrow?                    NOTE: British English

Shouldmild obligation — You should follow traffic laws when riding your bike.

recommendation, or advice — You should wear your helmet.

expectation — He should finish the race around noon.

Willfuture intent — I will go riding on Sunday.

promise — We will definitely make time to ride together next week.

prediction — The weatherman reports that it will be too windy to bike.

voluntary action — I will go anyway.

Wouldconditional — I would ride the bike at night if I had a headlamp.

past of will — He would ride his bike before he hurt his knee.


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