Grammar: Modal Verbs

Modals express our attitudes and emotions to an event or situation. The modal auxiliary verbs are: can, could, may, might, must, will, would, shall, should, ought to and need. There are other non-modal verbs and expressions (e.g. be able to, have to, allow) which we can sometimes use instead of modal verbs.

Form:

- Present time:

Subject + Modal + Infinitive: “You can go”

- Past time:

Subject + Modal + Have + Past participle: “You could have gone”

* Notes:

- “He/ She/ It can go” (there is no change in the third person)

- Modal verbs have no infinitive form.

TYPES OF MODALS:

1. Permission:

Can, could and may are used to talk about permission.

- Can:

“Can I go out? Is that all right?” (Asking for permission)
“He can go to the cinema on his own. That’s OK.” (Giving permission)

- Could:

“Could I borrow some money?” (Asking for permission - more polite than Can I...?)
“She said that I could go to the party” (Reporting permission)

- May:

“May I leave class early today? I’ve got a job interview.” (Asking for permission – for more formal situations)

Other non-modal verbs and expressions can be used to talk about permission:

- Let + Object + Infinitive:

“My parents let me go to concerts with my friends.”
(Note: Let does not have a passive form)

- Allow (to):

“They allow her to watch TV.” (Allow + Object + To + Infinitive)
“I was allowed to leave class early today.” (Passive + To + Infinitive)
(Note: In a sentence like this, where the permission resulted in an action, we can’t use could. E.g. “I could leave the class early today.”)

- Permit (to):

“You are permitted to smoke only in the designated areas.”
“Smoking is permitted only in the designated areas.”
(Rules made by someone else – more formal than allow)

2. Prohibition:

Can’t, couldn’t, mustn’t and may not are used to talk about prohibition.

- Can’t:

“He can’t go to a nightclub. He’s too young.” (Prohibition)

- Couldn’t (past form of can):

“He said I couldn’t use it.” (He refused permission)

- Mustn’t:

“You mustn’t talk in the library. Please be quiet!” (Direct order)
(Note: The past form of this sentence is “I wasn’t allowed to talk in the library”)

- May not:

“Candidates may not leave the room during the exam.” (Prohibition)

Other non-modal expressions can be used to talk about prohibition and rules that are made by someone else:

- Not supposed (to):

“You’re not supposed to park here.”

- Allow (to):

“My manager won’t allow me to take the day off.”
“You are not allowed to take photographs here.”

- Permit (to):

“You are not permitted to smoke in here”
“Smoking is not permitted here.” (More formal than allow)

- Forbid/ Ban:

“Cars are forbidden/ banned in the town centre.” (Prohibition – Very strong)
(Note: Forbid is more likely to be used in formal notices than when speaking)

3. Obligation and Necessity:

We use must/ mustn’t to express strong obligation or necessity.

- Must (stronger than should/ had better):

“I must post the letter straightaway.” (I, personally, feel it is necessary)

*Note: For the future of must we use will/’ll have to and for the past we use had to:

“I’ll have to hurry or I’ll miss the last bus”. (Future)
“She had to go home because she felt ill.” (Past)

- Mustn’t (stronger than shouldn’t):

“You mustn’t forget your keys.” (An obligation NOT to do something.)

Other non-modal verbs can be used to talk about strong obligation and necessity:

- Have (got) to is used when the situation or someone else (not the speaker) makes it necessary:

“I have to work late tonight. My boss says so.”
“We‘ll have to invite my mother next time.” (The situation makes it necessary)
“I had to go to the doctor yesterday.” (Past time – It was necessary)

- Make is used for a strong obligation imposed by someone else:

“Her parents make her wash the dishes.” (Make + Object + Infinitive)
“She is made to wash the dishes.” (Passive + To + Infinitive)

Should/ Shouldn’t, Ought to/ Ought not to are used to express a slightly less strong obligation or a duty/ responsibility:

“You should/ ought to phone and let them know you’ll be late.”
“They shouldn’t leave without permission.”

Should have/ Ought to have is used when something was the right thing to do, but you didn’t do it:

“You should have/ ought to have had an early night last night. You look tired.” (You didn’t go to bed early)
(Note: shouldn’t have is commonly used, but ought not to have is rare)

Supposed to is a non-modal expression we use to talk about our responsibilities and the correct way of doing things:

“What time are we supposed to be at the office?”

4. Lack of obligation/ necessity:

We use don’t have to/ Haven’t got to, Needn’t/ Don’t need to, Needn’t have and Didn’t need to to express lack of obligation or necessity.

- Don’t have to/ Haven’t got to:

“You don’t have to wash those dishes. They’re clean.” (It’s not necessary)

*Note:
Have got to is more informal than have to. We use didn’t have to as the past form of both don’t have to and haven’t got to:
“I didn’t have to go to the doctor’s yesterday.” (It wasn’t necessary)

-Needn’t/ Don’t need to:

“You needn’t/ don’t need to wash those dishes. They’re clean. (It’s not necessary)

*Note:
Need can be a modal verb (negative: needn’t) or an ordinary verb (negative: don’t need)

- We use both needn’t have (modal verb) and didn’t need to (ordinary verb) when we talk about past time, but they have different meanings:

“There were plenty of seats on the train. We didn’t need to stand.” (It wasn’t necessary)
“There were plenty of seats on the train. We needn’t have stood.” (It wasn’t necessary, but we did stand)

5. Advice and Recommendation:

Should (n’t)/ Should have, Ought to/ Ought to have are used o give advice and recommendations. (Ought to is less commonly used than should)

“You should see it. It’s a great film.”
“You shouldn’t/ ought not to go to work today. You really don’t look well.”

*Note:
The past forms should have/ shouldn’t have suggest criticism:

“You should have told me you weren’t coming, I waited for ages.”
“He shouldn’t have shouted at me.”

The non-modal expression had better (not) is stronger than should/ shouldn’t:

“It’s cold. You’d better wear a coat.” (It’s the best thing to do)
“Hurry up! We’d better not be late.”

6. Speculation and Deduction:

- Must (Certainty. We are sure it’s true):

“The lights are on. Harry must be at home.” (Present: Modal + Verb)

“Helen is late. She must have missed the train.”
“He must have been going to work. That’s why he was in a hurry.”
(Past: Modal + Have + Past Participle)

- Can’t/ Couldn’t (Certainty. We are sure it’s NOT true):

“Jamie can’t/ couldn’t be in the library. It’s closed.” (Present: Modal + Verb)
“It can’t/ couldn’t have rained/ been raining. The roads are dry.” (Past: Modal + Have + Past Participle)

- May/ Might/ Could (Possibility. We are less sure):

“Sally may/ might/ could be at home. I don’t know.”
“They may/ might/ could be watching us. Who knows?”
(Present: Modal + Verb)

“She may/ might/ could have left already. I’ll check.”
“The train may have been delayed.”
(Past: Modal + Have + Past Participle)

7. Ability:

Ways of expressing ability:

- Present: Can is more common than be able to in the present.

“Can you play tennis? No, I can’t.”

*Note:
Can also expresses future ability, if we are deciding now about the future.

“I can play tennis tomorrow if you want.”

- Past: Could/ Was able to

~ Use could for general past ability.

“Could you play chess when you were a child?”

~ Use was able to, not could, for ability in a specific situation.

“I was finally able to finish my model plane last weekend.”

~ Use wasn’t able to or couldn’t for both general and specific ability.

“I couldn’t/ wasn’t able to beat Tom at squash yesterday.”

- Future/ Perfect tenses/ Infinitive form: Can has no infinitive or past participle, so we use be able to.

“I will be able to play more tennis in the summer.”

“Has he ever been able to finish a marathon?”
“I might be able to go hiking next weekend.”

- Other ways of expressing ability:

“I know how to play chess.” (I have learned the skill)

“I succeeded in beating my sister last week.” (Suggests some difficulty)
“I managed to beat my brother as well.” (Suggests a lot of difficulty)


Exercise:

1. Complete this conversation with modals can, may, might, could, must and the correct form of the verb in brackets. There may be more than one possibility.

Modal verbs

Gap-fill exercise

Fill in all the gaps, then press "Check" to check your answers. Use the "Hint" button to get a free letter if an answer is giving you trouble. You can also click on the "[?]" button to get a clue. Note that you will lose points if you ask for hints or clues!

Jill: Our new designer jeans aren't in the warehouse. Have you any idea where they (be)?

Allan: No, but they (be) in the shop. Shall I ring and find out?

Sue: No, they (be) there. The shop's closed for the weekend. Someone (steal) the jeans from the warehouse during the night. That's the only possible explanation.

Allan: But how (the thieves/ get in)? They (break in) through the window, because there's an alarm.

Sue: They (have) a key or we (leave) a door unlocked by mistake, or perhaps someone (hide) in the warehouse when we left last night.

Jill: I'm sure there (be) some other explanation.

John: Good morning everyone! Guess what? I sold our new jeans collection to a private buyer last night...Why are you looking at me like that?