Grammar Tips: What Are Modal Verbs?
  • 3-minute read
  • 30th June 2021

Grammar Tips: What Are Modal Verbs?

Modal verbs are a special category of verb in English. But how do they work? And how should you use them in your writing? In this post, we explain the basics.

How Are Modal Verbs Used?

Modal verbs are a type of auxiliary verb. These are “helping” verbs that work alongside other verbs to help us express something. Modal verbs in English include “can,” “may,” “must,” “should,” “would,” “might,” and “will.”

Typically, we use a modal verb before another verb to express one of four things:

  • Possibility or likelihood (e.g., It might rain later today).
  • Ability or capacity for something (e.g., Birds can fly).
  • Obligation (e.g., You must finish your work today).
  • Permission (e.g., She may eat another slide of cake).

You can also form a question by switching the subject and modal verb in a sentence. Take the following example, for instance:

Statement: You can jump very high!

Question: Can you jump very high?

Here, placing the modal verb “can” before the subject “you” lets us frame the sentence as a question rather than a statement.

Strength and Formality

The best modal verb to use will often depend on two things: the strength of the claim you are making, and the level of formality you’re trying to achieve.

For example, traditionally, “may” expresses a greater degree of likelihood than “might.” As such, “It may rain” would be a stronger claim about what the weather will do than “It might rain.” But “will” is stronger than both, implying certainty.

And while we can use “may,” “could,” or “can” to ask for or grant permission, these terms imply different levels of formality. For instance:

Formal: May I ask you a question?

Less formal: Could I ask you a question?

Informal: Can I ask you a question?

This makes it important to pick your modal verbs carefully, especially in formal writing. If you’re not sure how a modal verb is used, check online.

Negative Forms of Modal Verbs

To negate a modal verb, you typically just need to add “not” after the verb:

He will not listen to you.

They should not speak to her like that.

A slight exception to this is “cannot,” which is always written as a single word:

We cannot afford a new car until next year.

In all cases, though, negating a modal verb expresses the opposite of what it usually would. For example, saying someone “cannot” do something means they’re not able or not permitted to do it (whereas “can” means they are able or permitted).

These negations can often be contracted into a single, shorter term. For example:

Uncontracted Negative





We can’t afford a new car.

could not


You couldn’t hear her.

will not


They won’t disturb you today.

would not


She wouldn’t tell me the secret.

should not


He shouldn’t go out without a coat.

must not


You mustn’t tell your mother that!

However, you shouldn’t use contractions in formal writing. For example, in a student essay or business document, you would want to write “cannot” in full.

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