Modal Verbs: The Only Guide You Need!

Modal verbs are used to express modality. Modality is the speaker’s attitude towards a specific situation. Examples of these attitudes are: ability, certainty, obligation, possibility, impossibility, advice, permission, prohibition, invitations, offers, and requests.

Here are the most common modal verbs:

can	could
may	might
shall	should
will	would
must	ought to and had better*

* These verbs are frequently referred to as semi-modals

These modal verbs have some important features:

They do not inflect: you don’t use the third person singular -s.
You use the bare infinitive of verbs following them (infinitive without to, ‘to’ only appears with ‘ought to’)
They function like auxiliary verbs, which means that you have a subject-verb inversion in questions
To make them negative, you add not in front of them

Ability

Use can to express ability or skills in the present. Its negative forms are can’t or can not/cannot.

He can speak English.
You can’t sing very well.
Can your sister swim?.

Use could to express ability or skills in the past. Its negative forms are couldn’t or could not.

I could run a marathon when I was younger.
They couldn’t find the place they were looking for.
Could he drive a truck?

Note that we don’t have a future form for ‘can’, so we use the expression be able to in the future instead:

In 5 years, I will be able to speak one more language.

If we want to say that we had the ability or the opportunity to do something in the past, but we didn’t, we use could have:

I could have caught the bus [but I chose not to].
My family could have lived abroad [but we chose not to].

Certainty

If you are sure about something, you can use must to express certainty in the present:

You haven’t eaten all day. You must be starving!
It is summer in Brazil. It must be quite hot.

Should can be used when we believe something is true in the present:

Why don’t you ask your brother to lend you some money? He should do that for you.
I don’t have the information you need, but Mark should be able to help you.

For the past, use must have and should have:

When we left her house, it was dark. It must have been very late.
Ben failed the final test. He should have studied more.

Obligation

If you want to say that something is mandatory, use must or mustn’t/must not:

If you work there, you must wear a uniform.
People mustn’t smoke here.

If this obligation was in the past, use had to:

I worked there, I had to wear a uniform.
I worked there, I didn’t have to wear a uniform.

Possibility

When we want to say that we are not certain about something, but the situation is possible, we use may, might, can, and could:

You may meet Sandra at the store if you go there now. She works there.
The sky is getting so cloudy. It might rain later.
You could get the flu if you don’t wear a coat.
Walking on the streets alone at this time can be very dangerous.

Impossibility

Can’t or can not/cannot express impossibility in the present:

It can’t be happening!
They cannot do that.

For the past, use can’t/can not/cannot have or couldn’t/could not have:

I told him this morning what he should do. He can’t have forgotten!
She was the best student in our class. She couldn’t have failed any subjects.

Advice

To make suggestions or give advice, use should or shouldn’t/should not. Had better and ought to are other options you have instead of ‘should’:

You should go to this event. It will be very important for your résumé.
You had better go to this event. It will be very important for your résumé.
You ought to go to this event. It will be very important for your résumé.
You shouldn’t lie to me. If you ever do that again, you will be grounded.
You had better not lie to me. If you ever do that again, you will be grounded.
You oughtn’t to lie to me. If you ever do that again, you will be grounded.

Permission

Can, could, and may are used for asking for permission to do something. The first is the most informal, the second is more neutral and the third is more formal:

Can I go to the restroom, Ms. Clark?
Could I invite some friends to come home and watch a movie?
May I see Dr. Smith?

In giving or refusing permission, we use can, and may. The levels of formality of both modal verbs are the same:

Yes, you can go.
No, you can’t go.
Sure, you may see him in a moment.
I’m sorry, but you may not. He’s in a very important meeting at the moment.

Prohibition

If you want to say that someone is prohibited from doing something, use mustn’t/must not for the present or couldn’t for the past:

People mustn’t enter this area.
You must not press this button.
People couldn’t smoke there.

Invitations

When inviting someone to do something, use would or must. ‘Must’ is more formal than ‘would’:

Would you like to go to the party with me?
You must come to dinner tomorrow.

Offers

If you want to offer someone help, use can, shall, could, or will:

Can I help you?
Shall I carry these bags for you?
Could I take you to work today?
I will do that for you if you like.

Requests

To make requests, use may, could, would, can, and will. These modal verbs are in a sequence from the most formal (may) to the most informal (will):

May I sit down, please?
Could you close the window, please?
Would you help me with the reports tomorrow, please?
Can you help me with the homework?
Will you wash the dishes?

Summary

MODAL VERB	MEANING	EXAMPLE
can	1. ability in the present; 2. (im)possibility; 3. permission; 4. offer; 5. request	1. He can speak English; 2. It can/can’t be dangerous; 3. Can I go to the restroom?; 4. Can I help you?; 5. Can you help me with the homework?
could	1. ability in the past; 2. (im)possibility; 3. permission; 4. offer; 5. requests	1. Could he drive a truck?; 2. She could/couldn’t have failed any subjects; 3. Could I invite some friends to come home and watch a movie?; 4. Could I take you to work today?; 5. Could you close the window, please?
had better	advice	You had better go to this event. It will be very important for your résumé.
may	1. possibility; 2. permission; 3. requests	1. You may meet Sandra at the store if you go there now. She works there; 2. May I see Dr. Smith?; 3. May I sit down, please?
might	possibility	The sky is getting so cloudy. It might rain later.
must	1. certainty; 2. obligation; 3. prohibition	1. You haven’t eaten all day. You must be starving!; 2. People mustn’t smoke here; 3. People mustn’t enter this area.
ought to	advice	You ought to go to this event. It will be very important for your résumé.
shall	offers	Shall I carry these bags for you?
should	advice	You should go to this event. It will be very important for your résumé.
will	requests	Will you wash the dishes?
would	1. invitations; 2. requests	1. Would you like to go to the party with me?; 2. Would you help me with the reports tomorrow, please?

Other verbs

Other verbs, such as need and dare, may be used as modal verbs. Thus, you could see sentences such as:

She needn’t/need not to work tomorrow (instead of ‘She doesn’t need to work tomorrow’).
You daren’t/dare not say that again! (instead of ‘You don’t dare to say that again!’).

In general, their uses as modal verbs appear in more formal English, usually in writing.

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