How to Use Modal Verbs for Clear Communication

Admin / August 3, 2024

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You likely found this post by asking “What’s a modal verb?”. In short, modal verbs are used in English to express possibility, permission, necessity, ability, obligation, and probability. But they can be confusing because they’re different from other verbs.
Mastering modal verbs is essential to communicating clearly and accurately in English, and I’m here to help. As a former English teacher and now freelance copywriter, I’ll draw on my experience to explain what modal verbs are and how to use them with confidence so your writing can really sparkle.

Key Takeaways

  • Common modal verbs include “can,” “should,” “might,” “must,” and “will.” 
  • Modal verbs help you express possibility, permission, necessity, ability, obligation, and probability.
  • A modal verb goes before a main verb and doesn’t change according to the subject of the sentence (who is doing the action). 
  • Semi-modal verbs can behave like modals or regular verbs — common examples include “need”, “dare”, “ought to”, and “used to”.
  • Using an AI proofreading tool can help you check if you’ve used modal verbs correctly.

Summary of common modal verbs

Here’s a list of the most common modal verbs you can use — many of them in more than one context:

Common model verbs

What’s a modal verb?

A modal verb is a type of verb that expresses possibility, permission, necessity, ability, obligation, and probability. Common modals include “can,” “could,” “must,” “should,” “would,” “will,” or “may,” but we’ll explore them fully below.
A modal verb comes before a main verb to alter its meaning.
In this example, the modal verb, “can,” is in blue. The main verb is in red.
  • He runs
  • He can run
The first example is an action that takes place. The second example suggests the possibility of the action taking place – either that the person has the ability to run or has permission to do so. 
Note also that the modal verb itself doesn’t change depending on who is doing the action:
  • She might run
  • They should run
  • It must run
The main verb is in its base form (“run”) rather than changing to the first-person singular (“runs”). The base form is also known as an infinitive without to (e.g. “to run” becomes “run”, “to sing” becomes “sing”, and “to be” becomes “be”).
When we want to create a negative, we add the word “not.” 
  • He does not run
  • She cannot run (or she can’t run)

Semi-modal verbs

“Need” and “ought to” are generally referred to as “semi-modal” verbs and are often used to express obligation and necessity.
“Need” can function as a pure modal verb or a main verb. However, it’s rare to use “need” as a modal, and even then, it tends only to be used in the negative or question form. When it’s used in the affirmative, it’s generally with a negative subject such as “nobody.” The example sentences below sound old-fashioned as a result:
“No one need speak.”
“You needn’t speak.”
“Need they speak?”
Nowadays, it’s more usual to use “need to” as a main verb followed by an infinitive to express necessity:
“I need to speak.”
“He doesn’t need to speak.”
“Do we need to speak?”
“Ought to” is semi-modal because, unlike full modal verbs, it always takes “to” before the infinitive. However, it doesn’t change according to the subject:
  • I ought to go to the store.
  • He ought to go to the store.
And the negative and question form are structured like full modal verbs. However, they’re rarely used and sound very formal:
  • He oughtn't to go to the store
  • Ought he to go to the store?

Using modal verbs to talk about the past, present, and future

All modal verbs can refer to the present or future without changing. So, for example:
  • I must clean the flat now. (Present)
  • I must clean the flat tomorrow. (Past)
Only some modal verbs can refer to the past, e.g. “could” and “would.”
  • He could run for miles in his youth.
  • She would run to school every day.
We can also talk about the hypothetical past using the modal with the verb “have” and the past participle. For example:
  • We could have won the prize. (We had the opportunity to win the prize, but we didn’t).
  • She might have passed the leader. (She had the opportunity to pass the leader, but she didn’t).
For a continuous action, we use the modal with the verb “be” and the -ing form of the main verb. In the present, this looks like:
  • I may be coming to the show.
In the past, this looks like:
  • He must have been frightening.

When are modal verbs used? 

Modal verbs are used to express possibility, permission, necessity, ability, obligation, and probability. As you’ll see below, some modal verbs can perform more than one of these functions.

Possibility

Modal verbs can help you express the degree of likelihood that something will happen. For example:
  • Might: There might be snow in December (weak possibility).
  • May: It may be rainy next week (slightly stronger possibility than “might”)
  • Could: He could be the winner of the contest (same as “might”)
  • Should: There should be cake at the party (strong possibility)

Permission

When we want to show that we have permission, we use the following modal verbs:
  • Can: Yes, you can use my pencil. 
  • May: He may take a place on the Council. 
  • Could: I was told I could have lunch at 1pm. 
We can also use the modal verbs to ask for permission:
  • Can: Can we get a map?
  • May: May I sit here? (More formal than “can”).
  • Could: Could I ask you a question? (Tentative and polite)
  • Might: Might I trouble you for a glass of water? (Very tentative and polite)

Necessity

We use the following modal verbs to convey how important it is for something to happen:
  • Must: I must complete my assignment by June.
  • Should: I should go to bed early (usually a milder necessity).
We can also use the semi-modal “need to” for this purpose:
  • Need to: We need to pick up the children soon. 

Ability

We can use modal verbs to express our ability to do something, such as:
  • Can: I can play the piano (present tense ability).
  • Could: I could play the piano when I was a child (past tense ability). 
We can also use modal verbs to modify the phrasal verb “to be able to” to show when the ability is tentative or speculative:
  • May: He may be able to come too.
  • Might: I might be able to call him today. 

Obligation

Modal verbs can express duty or responsibility. This is similar to necessity but can capture more of an external requirement. For example:
  • Must: You must be home by midnight (external requirement from a parent or guardian). 
  • Should: He should say sorry to his sister (social external requirement).
Semi-modals can also be used here: 
  • Ought to: They ought to take the issue seriously (a more formal sense of duty).
  • Need to: I need to make sure my cat is okay (responsibility).

Probability

Modal verbs can express how likely it is that something will happen:
  • Must: He must be at home by now (strong probability).
  • Should: I should have the report finished by Friday (moderate probability).
  • Might: They might be at the party (uncertain probability). 
  • Could: It could rain at the weekend (hypothetical situation). 
  • May: He may bring a friend to the dinner (uncertain probability).

Emphasis

You can also place emphasis on modal verbs to convey your meaning with particular strength. For example:
  • I can get through this! (Suggests determination)
  • You might get a treat from me if you do your best (Sarcastic use – implies they will, in fact, get a treat)

Future tense

The modal verb “will” is how we commonly express the future tense in English. For example:
  • I will go to work on Monday.
  • They will reach Kyoto in two days. 

How to check if you’re using modal verbs correctly

Once you’ve completed a piece of writing, it’s important to proofread carefully, including for grammatical errors. If you’re still not sure whether you’re using modal verbs correctly, try using AI software like Rewritai to find and correct any mistakes. 
This can be much quicker and easier than checking yourself, as the software will automatically find and highlight any mistakes as well as giving a correction.
Conclusion 
Now you know that modal verbs can be added to main verbs to help you convey possibility, permission, necessity, ability, obligation, and probability. They can also be used in different grammatical moods, such as the subjunctive, and to form the future tense with “will.”

Remember that modal verbs go before a main verb in the infinitive (without to) and don’t change according to the subject of the sentence (who is doing the action). They also don’t have tenses in the same way as other verbs. Finally, in addition to full modal verbs such as “might” or “can”, there are semi-modals that can behave both as modals and as main verbs verbs, for example, “need to” and “ought to.” 
For more grammar tips, check out our blogs on double negatives and compound sentences.

FAQ

What are some common modal verbs?

‍Common modal verbs include “can,” “could,” “will,” “may,” “might,” “shall,” “should,” and “must.”

How do you identify the modal in a sentence?

‍The modal verb will go before the main verb to convey a sense of possibility, permission, necessity, ability, obligation, or probability. 

What is the rule of modals?

‍A modal verb won’t change according to the subject of the sentence and doesn’t have different tenses (past, present, future, etc).