Modal Verbs: Key Types and How They Function

You probably already know that verbs are words that convey action. But what action do modal verbs such as can, might and should convey? How do they fit into a sentence? Learn all about modal verbs with a helpful explanation and clear grammatical examples.

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What Is a Modal Verb?

Modal verbs are auxiliary verbs, also known as helping verbs. They work with other verbs to show various conditions, such as possibility or necessity. Modal verbs do not change form based on the verb tense of the sentence; they do not have conjugated forms.

The modal verbs in English are:

  • can

  • could

  • may

  • might

  • must

  • shall

  • should

  • will

  • would

Modal verbs can only function on their own if the main verb is obvious. For example, the sentence “Taylor can” doesn’t make sense on its own. But when it follows the sentence “Who can help me?” then the reader understands that the sentence is really “Taylor can help.”

Examples of Modal Verbs in Sentences

You see modal verbs everywhere you look — probably without even realizing it! Modal verbs show modalities such as possibility, necessity, ability, permission, and suggestion. Some can be used in many different ways, while others only work in one or two contexts.

Modal Verbs of Possibility

The modal verbs could, may and might indicate that there is a possibility or probability that something will happen.

  • I could pass this class.

  • Jason may bring chips to the party.

  • My parents might say yes.

  • You could get hurt.

  • Lola may change her mind.

When you exchange these verbs for other modal verbs, such as will and shall, they indicate a promise or certainty that something will happen.

  • I shall pass this class.

  • Jason will bring chips to the party.

  • My parents will say yes.

  • You will get hurt.

  • Lola will change her mind.

You’ll often find modals used this way in the conditional mood, which states that something might happen if another event happens as well. For example, “I could pass this class if I study” changes the possibility (passing the class) based on what needs to happen first (studying).

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Modal Verbs of Necessity

You can use the modal verb must or should to indicate that something needs to happen. It functions like the expression “have to” to show an obligation or necessity. When you add “not,” it indicates that something should not happen.

  • I must learn to drive.

  • We should work together.

  • The teacher should extend the deadline.

  • Katie must work harder.

  • My sister must feed her dog.

Notice that the degree of need depends on the modal you choose. “I must learn how to drive” has a higher need than “I should learn how to drive.”

Modal Verbs of Ability

Can is the main modal verb that shows one’s ability to do something. If you can replace can with “able to,” it’s being used as a modal of ability. Its negative form, cannot (or can’t), shows the opposite.

modal verb example sentence
  • I can swim well.

  • Our class can’t solve the math problem.

  • We cannot beat the other team.

  • Percy can hold his breath for two minutes.

  • Mr. Tracer can’t meet with you until tomorrow.

Could is a modal verb that shows one’s past ability. For example, “I could swim well as a child” indicates that the speaker could swim well in the past.

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Modal Verbs of Permission

Modal verbs can be used to ask permission or grant permission. These verbs include could, may, shall, and would. Granting permission usually uses the modal may.

  • Could I borrow your pencil? (Yes, you may.)

  • May I be excused? (No, you may not.)

  • Shall I take your coat? (Yes, you may.)

  • Would you mind if I sat here? (No, I wouldn’t.)

Some speakers add can to this list, as in “Can I spend the night at David’s house?” Strict grammarians believe that may is the proper modal verb to use in these cases, as can is traditionally a modal of ability. However, the rules regarding can vs. may have loosened up to allow can as a modal of permission in informal cases.

Modal Verbs of Suggestion

Another use of modal verbs is to make suggestions. Use could, might, must, and should to make a suggestion or give advice, often with the verbs “want to” or “consider.”

  • We could split a pizza.

  • You might want to wait until tomorrow.

  • Tim must consider a third option.

  • You should wear a coat today.

You can also use modal verbs of necessity in imperative sentences. Must and should are commonly found when a speaker gives advice or makes commands.

Past Modal Verbs

You can even use modal verbs to think about past events! Past modal verbs, such as could, might, should, and would use the word “have” with a past participle to discuss something that was once possible, needed, able to be done, or permitted but no longer is.

  • I could have become a big star.

  • My boss might have been a little rude.

  • The teacher should have explained the homework better.

  • We would have helped you.

Past modal verbs such as may and might can also speculate about something that has happened. As in other modal examples, adding "not" makes the sentence negative.

  • John may have missed his plane.

  • Judith might have gotten lost.

  • We may not have seen the sign.

  • This might not have been the best idea.

Some modals, such as can and shall, don’t work as past modals. Use could have and should have in these cases.

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Future Modal Verbs

Will appears in all future verb tenses. Use will with a present tense verb to form the basic future tense.

  • Paula will know the answer next week.

  • I will call you tomorrow.

Form the future progressive tense with will, the word “be” and a progressive verb.

  • John will be driving all night.

  • Our team will be waiting for your reply.

You can create the future perfect tense with will, the word “have” and a past tense verb.

  • My sister’s baby will have arrived by then.

  • We will have finished the project by the time the concert starts.

And finally, the future perfect progressive tense comes from the modal will, the phrase “have been” and a present participle ending in -ing.

  • I will have been working here for 30 years in December.

  • Claire will have been playing the harp for seven years when she plays at the recital.

As you can see, these verb forms aren’t as common in everyday speech. But you may be surprised to find how often you hear will when referencing the future!

Verbs and Expressions That Function Like Modals

Does it seem like there are some words missing from the list above? Several English verbs and expressions function just like modals. They are sometimes called semi-modals, and they include:

  • be able to (We’ll be able to rest soon.)

  • dare (I dare not enter without permission.)

  • had better (You’d better ask for the day off.)

  • have to (I have to get an A on this test.)

  • ought to (Shannon ought to buy a new car.)

  • need to (We need to think of a plan.)

Some of these expressions, particularly ought to, are sometimes included in lists of modal verbs. However, they are less common and more conversational than modal verbs.

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Could Have, Should Have, Would Have

Modal verbs show intention, rather than action. When used with other verbs in the sentence, they can make your meaning as clear as you want it to be. Test your knowledge of modal verbs with an examination of may vs. might. You can also make sure you’re using can vs. could correctly in your writing and everyday speech.