Modal Verbs; 4 Simple Rules to Master Them

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Updated on: Educator Review By: Michelle Connolly

May, might, must, will, would, can, could, shall, and should are all modal verbs that we’re about to discuss in this article. Modal verbs can be used to express many things ranging from ability, possibility, obligation, and permission. What makes learning these verbs harder is that each modal verb could have more than one use, besides the fact that different modal verbs could be used in the same context (they have similar uses). In the following sections, we talk about modal verbs, what they are used for, and how to use them by following four simple rules.

Table of content:

What Are Modal Verbs?

Modal verbs are a subtype of a larger category of verbs in the English language known as auxiliary verbs. They are always followed by a main verb which is always in the infinitive form as follows:

  • Modal verb + main verb (infinitive form).

There are many modal verbs used in the English language for different purposes listed in the following sections. These include can, could, may, might, must, will, would, shall, should, and ought to. There are also other verbs that are used like modals, including have to, need, be supposed to, be able to, and had better.

Example sentences:

  • They would like an iced coffee.
  • Would you like a cup of tea?
  • He should go to the dentist.
  • Will you borrow this book?
  • You must be kidding.
  • It might happen.
  • You can leave.

Why do we Need Modal Verbs?

We need modal verbs to talk about many things depending on which modal verb we use. For example, may and might are used to express probability, while can and could are used to express ability. We discuss the different types of modal verbs and their usage in the following section in much more detail.

Can/ Could

Can and its past form could indicate the ability to do something. They could also be used to give permission or express prohibition (in the negative form). Can could be used in informal requests (if you are asking a friend of yours or a family member). On the other hand, could is used to make a polite request (if you are asking someone you don’t know).

Example sentences:

  • We can travel to outer space thanks to advancements in science.
  • Could you give me your phone number, please?
  • Can you turn the music down, please?
  • He couldn’t find his wallet last night.
  • She can go to school alone.
  • She can speak French.
  • I can play basketball.
  • You can’t park here.

Will/ Shall

Will and shall are both used to talk about the future. They are used to express probability, to predict a future event, to make an instant decision or to make a promise.

Although shall was used in the past with the first person pronoun (I and we) in place of will, its use nowadays is very limited and could be seen only in formal or very polite contexts.

When using shall in questions, its meaning differs greatly, and it then indicates suggestion.

Example sentences:

  • We will travel the whole world one day.
  • Will you buy a new house?
  • Shall we go to the beach?
  • Let’s go, shall we?


Would is used in many situations to express lots of things, as follows:

  • To indicate habits in the past (things you did regularly in the past).
  • In the second conditional for imaginary situations and also in the third conditional.
  • To express a preference.

Example sentences:

  • She would like to have a cup of coffee. (preference)
  • I would buy a new car if I had more money. (second conditional)
  • I would have bought a new car if I had saved more money. (third conditional)
  • I would often go shopping with my friends when we were young. (habitual action in the past)

May/ Might

May and might are both used to indicate the possibility of something happening. The main difference between them is that may denotes a stronger possibility than might. So if you think that something is very less likely to happen (in hypothetical situations), then use might. Also, may is more common in formal and academic language than might. May could also be used to make a polite request.

Example sentences:

  • We may go hiking tomorrow if it doesn’t rain.
  • She might finish her work by 5 PM.
  • He may need a flu shot.
  • It might rain tomorrow.
  • They might be right.
  • May I help you?

Must/ Have to/ Have got to

Must is used to express one of two things:

  • To indicate necessity (when something has to be done) or requirement.
  • To express certainty. (unlike may and might, which express possibility “uncertainty”). So if you’re sure that something is true, use must instead of may or might.

Have to and have got to are also used to express necessity, but must denotes a stronger necessity and gives a sense of urgency. That’s why we use must in formal rules and warnings.

Example sentences:

  • You must have a driving licence before you drive a car.
  • You must study medicine to become a doctor.
  • You must consider every possibility.
  • He must be home now. (certainty)
  • You have to talk to the manager.
  • I have got to pay the bills.

Should/ Ought to/ Had better (‘d better)

These three verbs are used to give advice or recommendations. Keep in mind that Ought to is more formal than should.

Example sentences:

  • You should drink enough water in hot weather.
  • She’d better rest in bed till she’s fine.
  • You should tell them the truth.
  • He ought to find a new friend.
  • We had better be on time.

Now it’s time for a fun video that shows you how to use modal verbs in real-life situations;

Modal verbs in English

How to Use Modal Verbs

Now after we learned the different modal verbs and their uses, it’s time to talk about the four simple rules you need to be aware of to master these verbs:

Rule Number One

Modal verbs are always followed by the Infinitive without “to”.

Correct: She should go to the doctor.

Incorrect: She should to go to the doctor.

Rule Number Two

Modal verbs are the same for all pronouns, and they don’t change with the subject (they don’t take “s” in the third person singular).

Correct: He must leave.

Incorrect: He musts leave.

Rule Number Three

Modal verbs don’t change their form with each grammar tense; there’s no past or future form of modal verbs. They have only one fixed form. But this doesn’t mean we can’t use them to talk about past events. In fact, we can use them to talk about the past, but in a special form.

We can add “have + past participle” after the modal verb to obtain the past form as follows:

  • Should – should have + pp.
  • Could – could have + pp.
  • Might – might have + pp.
  • May – may have + pp.
  • Must – must have + pp.
  • Ought to – ought to have + pp.

Note that the past form of must (must have + pp) doesn’t give the same meaning of necessity. So the verb that gives the same sense of necessity in the past is had to, and it is also the past form of have to.

Example sentences:

  • We might have taken the wrong road.
  • She could have been more kind.
  • I should have studied harder.
  • He may have been asleep.
  • It could have been worse.

Note that when we use should/ could/ ought to + have + pp, this means we didn’t do something in the past, and we regret it (we’re very sad we didn’t do it).

Rule Number Four

Modals take direct negative and question forms.

1. In the negative form, we just add “not” to the end of each modal verb as follows:

  • May – may not (no contraction available).
  • Might – might not (mightn’t).
  • Must – must not (mustn’t).
  • Have to – don’t have to.
  • Has to – doesn’t have to.
  • Will – will not (won’t).
  • Would – would not (wouldn’t).
  • Can – cannot (can’t).
  • Could – could not (couldn’t).
  • Shall – shall not (shan’t).
  • Should – should not (shouldn’t).
  • Had better – had better not.

Note that:

  • Have to doesn’t follow the same rule for modals since it’s not a modal but a verb that works like a modal one.
  • The negative form of have to (don’t have to) removes the necessity or obligation, while the negative form of must (mustn’t) keeps it.

Example sentences:

  • You mustn’t go there without permission. (obligation is still present)
  • You don’t have to book a table. (obligation is removed)
  • I looked for my keys everywhere, but I couldn’t find them.
  • She may not be at home tomorrow.
  • You’d better not be late again.
  • I can’t go to the party tonight.
  • You shouldn’t eat junk food.
  • He might not know.

2. And to form a question, we just swap the modal verb and the subject (the modal verb comes first, followed by the subject) as follows:

  • Could you close the window, please?
  • Can you open the door?
  • May I use your phone?
  • Can you speak Spanish?


That was our topic for today. We hope you found it useful to learn about modal verbs in English. If you want to learn more about the English language, then you should check out our website.

Don’t know where to start off?

Then, check out the tag “English” on our website, where you will find lots of fun articles that teach you all aspects of the English language; writing, speaking, reading, phonics and much more.

And if you’re more into watching videos rather than reading, we also got a Youtube channel where you can learn new things with fun animation videos, so give it a shot.

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The main references used in this article:

  1. English Grammar in Use, Fifth Edition, Units 26 – 37: Modals.
  2. Practical English Usage by Michael Swan, Section 7: Modal Auxiliary Verbs.
  3. Advanced Grammar in Use, Third Edition, Units 15 – 20: Modals and semi-modals.
  4. Practice Makes Perfect, Intermediate English Grammar for ESL learners, Chapter 6: Modal auxiliaries.

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