Lesson 19. Modal Verbs

Grammar Focus: Modal Verbs

Modal verbs are special helping verbs. They add meanings such as ability, possibility, permission, obligation, advice, certainty, prediction, or willingness to another verb.

Common modal verbs include:

can, could, may, might, must, shall, should, will, would

How Modal Verbs Work

Most modal verbs follow the same basic pattern:

subject + modal verb + base form of the verb

Important Rules

Modal verbs are different from ordinary verbs in several ways.

• Do not add an s in the third-person. Example: He can swim.
• Do not use do or does when making questions. Example: Can you help me?
• For the negative form, put not after the modal verb. Example: I should not go.
• Do not use to after a modal verb. Example: She must leave.
• They do not have an infinitive form.
• They do not have all the forms of ordinary verbs.

The following sections will discuss each of the modal verbs.

Can

The modal verb can is very common and means either to have the ability to do something or to have permission to do something.

1. Ability

We use can to say that someone has the ability to do something.

Form:

subject + can + base verb

Examples	汉语
I can speak English.
She can swim across the lake.

Questions

To form a question, put the subject of the sentence after can.

Examples	汉语
Can she swim?
Can you speak English?

Negative

To form a negative statement, use cannot or its common contraction can't.

Examples	汉语
She cannot swim.
I can't drive.

2. Permission

Can is also used to ask for or give permission.

Examples	汉语
Can I open the window?
You can leave early today.

Could

The modal verb could has several important meanings.

1. Past Ability

Could is the simple past of can and is used for general abilities in the past.

Examples	汉语
She could swim across the lake before she broke her leg.
I could swim when I was five.
She could speak French when she was a child.

2. Possibility

Could is used to say that something is possible.

Examples	汉语
She could swim across the lake if she wanted to.
It could rain tomorrow.
We could miss the train.

3. Polite Requests

Could is used very often to make polite requests.

Examples	汉语
Could you help me?	你可以帮帮我吗？
Could you open the door?

4. Hypothetical Situations

Could is also used to talk about an ability or possibility that depends on one or more conditions.

Examples	汉语
I could help you if I had more time.
We could go to the beach if the weather improved.

Could Have

Could have + past participle is used to talk about a possibility or opportunity in the past. Could have is often shortened to could've.

Examples	汉语
She could have won the race.
We could have gone to the concert.
Could she have swum across the lake?
She could've swum across the lake if she'd wanted to.
She could have taken the earlier train.
They could have forgotten about the meeting.

Forms of Can / Be Able

Unlike most verbs Can only has a present and a past tense. For other forms, be able is used. The following table shows the different forms that are used.

May

Possibility

May and might are both commonly used when something is possible but uncertain.

Examples	汉语
John may have an extra pen.
I may go to the concert.
I may not have time to eat dinner.
She may be able to help you.
It might happen.
I might not be able to do it.

Permission

May can also be used to ask for or give permission, especially in more formal situations. In informal situations, can is more commonly used to ask for or give permission.

Examples	汉语
May I go to the store?
May I have something to drink?
You may have one chocolate bar.

May Have and Might Have

May have + past participle and might have + past participle are both used to indicate that an event possibly happened in the past. Might have is often shortened to might've.

Examples	汉语
It might have happened.
I may have lost the keys.

Must and Have to

1. Obligation

Must and have to can both express strong obligation.

Examples	汉语
You must wear a seat belt.
I have to work tomorrow.
She has to pass the exam.
She must pass the exam, or she will fail the course.

Must is only used in the present tense. Have to is especially useful because it can change form for different grammatical contexts.

Form	Expression
Infinitive	to have to
Present	must / have to
Past	had to
Present perfect	have had to
Past perfect	had had to
Conditional	would have to
Future	will have to

Examples	汉语
She had to leave early.
I'll have to do it eventually.
She had to pass the exam to be able to pass the course.

2. Must for Strong Deductions

Must does not always express obligation. It can also express a strong conclusion based on what we know or observe.

3. Must Not and Don't Have To

Must not and don't have to have very different meanings.

Examples	汉语
We've been walking for two hours. We must be near the lake.
He must be almost at the lake by now.
I must be going too slow.

Must Not = Prohibition

Use must not or mustn't when an action is not allowed or it is very important not to do something.

Examples	汉语
You mustn't leave.
You mustn't bring food into the library.
We must not forget to lock the door when we leave.

Don't Have To = No Necessity

Use don't have to when something is not necessary. You can do it, but you are not required to do it.

Examples	汉语
You don't have to leave.
I don't have to bring my laptop.

Must Have

Use must have + past participle to make a strong deduction about the past.

Examples	汉语
I must have left my keys at home.
They must have known what would happen if they did that.
He must've forgotten about it.

Should

1. Advice and Recommendations

We commonly use should to give advice or make recommendations.

Use should + base verb. Do not use to after should.

Examples	汉语
You should get more exercise.
You should study more.
We should see the new film.

2. Asking for Advice

To ask for advice, put should before the subject.

should + subject + base verb?

Examples	汉语
Should I study tonight?
What should I do?
Should we leave now?

3. Negative Form: Shouldn't

Use should not or the contraction shouldn't to advise someone not to do something.

Examples	汉语
You shouldn't worry.
You shouldn't drive so fast.
We shouldn't spend so much money.

4. Expectations

Should can also express an expectation. In this use, we are saying that we think something will probably happen or that we expect a situation to be true.

Examples	汉语
The train should arrive soon.
They should be home by now.
The package should arrive tomorrow.

5. Ought To

Ought to has a meaning similar to should, especially when giving advice or talking about what is appropriate.

Examples	汉语
You ought to get more sleep.
We ought to help them.

For most everyday situations, you can use should.

Shall

In everyday English, shall is most useful in questions with I and we. We commonly use it to make suggestions and offers.

Like other modal verbs, shall is followed by the base form of the verb without to.

1. Making Suggestions

Use shall we + base verb? to suggest doing something together.

Examples	汉语
Shall we go?
Shall we start?
Shall we eat outside?
Shall we invite Marta?

2. Making Offers

Use shall I + base verb? when you offer to do something for someone or ask whether they want you to do something.

Examples	汉语
Shall I open the window?
Shall I help you?

Note: Can I ... and Would you like me to ... are both more common ways to offer to help someone.

Will

Will + base verb is one of the most common ways to talk about the future. It expresses predictions, promises, spontaneous decisions, and things we believe will happen.

The common contraction of will after a subject is 'll.

1. Predictions and Future Events

Use will when you predict or expect something to happen in the future. Will often pairs with adverbs of probability like probably, definitely, certainly, or maybe.

Examples	汉语
We will talk about it later.
I'm sure it will work.
He will probably arrive soon.
We'll have time for dinner.

2. Spontaneous Decisions

Use will when deciding something at the moment of speaking.

Examples	汉语
I'll get the door.
I'll call you tomorrow.
That sounds good. I'll come!

Offers and Promises

Will is often used when making a promise, offer, or commitment to someone.

Examples	汉语
I will help you with your homework.
We'll take care of everything.

Negative Form

The negative form is will not, which is commonly contracted to won't.

Examples	汉语
We won't have time for dinner.
It won't work.
They won't finish on time.

Questions

To form a question, put the subject of the sentence after will.

Examples	汉语
Will you go shopping after work?
Will they come tomorrow?
What will you do?

Would

Would has several important uses. The two most common are hypothetical situations and polite requests.

1. Hypothetical Situations

Use would when talking about imaginary or unlikely situations. This is often paired with an if-clause.

Would is often contracted to 'd

Examples	汉语
I'd go to the concert if I had more money.
We would buy the house if it were cheaper.
She would travel more if she had vacation time.
She'd help us if she could.
They would help if they knew the truth.
I'd learn Italian if I lived in Rome.

2. Polite Requests

Would is also common in polite requests.

Examples	汉语
Would you help me?
Would you open the window, please?

Past Habits

Would can also describe repeated habits or actions that happened in the past but do not happen now. It has the same meaning as used to.

Examples	汉语
When I was young, I would play outside every day.
We would visit them every summer.

Negative Form

Would not is usually contracted to wouldn't.

Examples	汉语
I wouldn't do that.
They wouldn't agree.