What are modal auxiliary verbs?

Modal auxiliary verbs, also commonly referred to as modal verbs or modals, are used to shift the meaning of the main verb in a clause. These shifts include expressing possibility, ability, permission, obligation, or future intention. Students can find these confusing because one modal auxiliary verb can have multiple meanings depending on the context.

There are two categories of modal auxiliary verbs: pure modal auxiliary verbs and semi-modal auxiliary verbs.

There are nine pure modal auxiliary verbs: will, shall, can, could, may, might, must, would, and should.

Semi-modal auxiliary verbs like ought to, had better, have (got) to, be able to, used to, and be supposed to can have modal meanings, but they don’t follow the same rules as pure modal auxiliary verbs.

Many sources and student textbooks do not differentiate between pure modal auxiliary verbs and semi-modal auxiliary verbs, and others separate them completely.

Pure Modal Auxiliary Verbs

What makes it a “pure” modal auxiliary verb?

The nine pure modal auxiliary verbs, will, shall, can, could, may, might, must, would, and should, share the same characteristics.

Modal auxiliary verbs are followed by a main verb in its bare infinitive form (the infinitive form without to).

Students should arrive early.
Students should to arrive early.

Modal auxiliary verbs do not have an infinitive form.

I might go to the party tomorrow.
I to might go to the party tomorrow.

The modal auxiliary verb and the main verb do not conjugate for tense or the third-person singular.

Peter can play the piano.
Peter cans play the piano.
Peter can plays the piano.

The adverb not is used with the modal auxiliary verb to create negative sentences.

Students shouldn’t arrive early.
Students should arriven’t early.

To make an interrogative sentence (question), the modal auxiliary verb is inverted with the subject. No other auxiliary verbs are added to make questions.

Students should arrive early. (affirmative sentence)
Should students arrive early? (interrogative sentence)
Do students should arrive early?

Principal meanings of the modal auxiliaries with examples

There are many more uses for the modal auxiliary verbs listed below. These are just some of the most common ones. If we missed something that should be added, please leave a comment below!

Can

Usage	Example
Present Ability	I can play the piano.
Asking Permission	Can I leave now, Mrs. Jones?
Granting Permission	You can go after you finish your homework.
Possibility	We can join the tour. There are a few spaces left.
Negative Certainty	That can’t be my brother. He’s in Japan.
Polite Request	Can you pass the salt, please?
Polite Offer	Welcome to McDonald’s. Can I take your order?

Could

Usage	Example
Past Ability	She could play the piano when she was 10.
Asking Permission	Could I bring a friend to your party?
Possibility	My keys could be locked in the car. They are not in my purse.
Polite Request	Could you lend me a hand?
Polite Offer	I could drive you to the airport.
Making Suggestions	We could order a pizza for dinner tonight.
Choices or Opportunities	You could fly alone, or we could take the train together.

May

Usage	Example
Asking Permission	May I have more time to finish my project?
Granting Permission	You may leave when you finish your homework,
Polite Offer	How may I help you?
Possibility	The boss may be late today.
Express Future Wishes	May we continue to be healthy for many years.

Might

Usage	Example
Asking Permission	Might we borrow your car this weekend, mother?
Making Suggestions	You might try taking the subway to work.
Possibility	We might have enough money by the end of the year.
Contrasting Statements	I might be new, but I have the experience to do it right.

Must

Usage	Example
Necessity	You must register before we can proceed.
Strong Intention	I must tell him the truth.
Strong Suggestion/Recommendation	You must visit us again!
Expressing Certainty	There must be a way to make everyone happy.

Should

Usage	Example
Polite Obligation	Guests should wear formal attire.
Suggestion or Advice	You should eat more fruit.
Expectations	My order should be ready now.

Will/Shall

Will is becoming much more common than shall, and this trend seems to be continuing. It is seldom used in American English. The next two tables illustrate some of the similarities and differences between these two modal auxiliary verbs.

Usage	Example
Future Simple Tense	I will take the bus this evening.
Future Perfect Tense	At the end of the month, we will have been married for 10 years.
Future Perfect Continuous Tense	By next summer, I will have been studying French for a decade!
Decision at the Moment	Um, I will take the red one.
Offers	I’ll send the package for you.
Requests	Will you drive me to the airport? Shall you drive me to the airport?
Forceful Commands	You will clean up your room right now!
Promises	I will always love you.
Predictions	My team will win the championship.

Usage	Example
Future Simple Tense	I shall take the bus this evening.
Future Perfect Tense	At the end of the month, we shall have been married for 10 years.
Future Perfect Continuous Tense	By next summer, I shall have been studying French for a decade!
Offers (I/We)	Shall I call a taxi for you? Will I call a taxi for you?
Make Suggestions (I/We)	Shall we see a movie tonight? Will we see a movie tonight?
Formal Commands	Members shall pay their dues each month. Members will pay their dues each month.
Promises	The company shall do everything to help you succeed.
Predictions	I shall be the manager one day.

Would

Usage	Example
Future Expectation	I thought my package would be here by now.
Past Ability/Willingness	Sorry I’m late. My car wouldn’t start this morning.
Polite Requests	Would you make sure the door is locked before you leave?
Express Desires	I would like to live near the beach.
Hypothetical Situations	She would join us, but she has a tight deadline at work.
Polite Advice	I know you failed, but I would try again.
Past Habits	My old teacher would always tell us to study hard.

Semi-Modal Auxiliary Verbs

Let’s take a look at ought to, had better, have (got) to, be able to, used to, and be supposed to. We’ll explain some of the reasons why these are not always categorized as modal auxiliary verbs. You’ll also see some examples demonstrating their modality.

ought to

The semi-modal auxiliary verb ought to ends in to, which makes the main verb an infinitive. This differs from pure-modal auxiliary verbs, which use the bare infinitive, the infinitive without to, for the main verb. The meaning of ought to is nearly the same as should in all cases. When forming questions or negatives, should is more commonly used than ought to.

Usage	Example
Suggestion or Advice	You ought to eat more fruit.
Expectations	My order ought to be ready now.

had better

Had better is a two-word semi-modal auxiliary verb that has the same characteristics as pure modal auxiliary verbs.

Usage	Example
Strong Suggestion – otherwise there will be negative results	You’d better bring a jacket or you will catch a cold.

have to / have got to

Have to and have got to break all of the rules that pure modal auxiliary verbs follow. They consist of more than one word, they use infinitive forms of the main verbs, the auxiliary verb do is used for negatives and questions (for have to, not for have got to), and they conjugate for the third-person singular. Despite all of these differences, these semi-modal auxiliary verbs have several modal meanings.

Usage	Example
External Obligation	We have to pay taxes. We have got to pay taxes.
Strong Suggestion/Recommendation	You have to try the new French restaurant. You’ve got to try the new French restaurant.
Expressing Certainty	This has to be the right place. This has got to be the right place.

be able to

The semi-modal auxiliary verb be able to shares meanings with the pure modal auxiliary verb can.

Usage	Example
Present Ability	He is able to swim.
Asking Permission	Are we able to leave before the bell rings?
Granting Permission	You are able to leave the classroom after you finish your work.

be going to

Be going to is a semi-modal auxiliary verb that has two basic meanings. The first meaning describes plans, intentions, or decisions for the future. We also use be going to for predictions when we are 99.9% sure about the future based on present facts.

Usage	Example
Future Plan	We‘re going to move to New York next month.
Predictions	My car broke down. I am going to be late.

used to

To talk about past habits or conditions that are no longer true in the present, we use the semi-modal auxiliary verb used to. The past form of the auxiliary verb do is used when forming negatives and interrogatives.

Form	Example
Affirmative	I used to live downtown, but now I live in the suburbs.
Negative	The teacher didn’t use to give us homework.
Interrogative	Did you use to have a mustache?

be supposed to

Be supposed to is used to describe things that people are expected to do, or for things that are generally believed.

Form	Example
Expected Actions	You are supposed to take a shower before entering the pool.
General Beliefs	Running every day is supposed to help you lose weight.

Learn more about different types of verbs

Learning about different kinds of verbs can enhance your understanding of English.

Let us know what you think!

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