English Grammar

Modal verbs of probability in English with illustrations

Modal verbs of probability

Modal verbs of probability can be intimidating for those learning to speak in English. But, the reality is that they are verbal structures that are found daily in both spoken and written language . Modal verbs of probability in English

For example, if you are watching or reading the news and you discover information that you find incredible, you may say “That can’t be true!” (That can not be true!). This sentence includes a modal verb of probability. Thus, modal verbs help add information to the sentence .

If you practice enough, in no time you will learn to use this important grammar resource. Discover in this lesson what are the modal verbs of probability and the uses we can give them .

What is a modal verb?

Before we get into the topic of modal verbs of probability, let’s have a better understanding of what a modal verb is. The dictionary defines it as an auxiliary verb that expresses probability or necessity . They are also commonly used with other verbs to help convey possibility, ability, obligation, belief , among others.

Modal verbs of probability

They are used to convey the probability or possibility that a particular event occurs, or whether it is true or not . These verbs have different degrees of probability. Some express absolute certainty, while others indicate that something is less likely.

Must and Can’t

They are modal verbs of strong probability . We use them to speak with total certainty of a matter, it can be to affirm or to deny. If we want to absolutely affirm a fact, then we use the verb “must” .

  • He must be really handsome for Ana to lose her head this way.
  • Tim is not here. He must be working in the factory.

If we want to deny an issue with complete certainty, we use cannot (can’t). We cannot use “must not” because it behaves as a modal verb of prohibition.

  • He can’t be at home, I saw him running at the park.
  • Surely he can’t be serious!


“Should” indicates that there is a great possibility that something will happen or that we are very certain that it will happen . It is a way of expressing the probability if everything goes as planned. It conveys the idea of: “if everything goes according to plan”.


  • She is ten minutes away. She should be there are.


It is the modal verb of probability that serves to affirm. It is translated in English “can” and expresses that an event is possible but there is a certain degree of uncertainty. It has a lower degree of probability than that transmitted with “should”. Modal verbs of probability in English


  • Smoking can cause you respiratory problems such as cancer.
  • Loud music can be a problem when you are living in an apartment.

Could, may and might

These three modal verbs are those that serve to speak of a weak probability . They indicate that something is likely to happen in the future, but with a degree less likely than “can.”


It tells us about the probability that something is happening or is about to happen .


  • may not get this job.
  • It may not rain tomorrow.
  • There may be some evidence to suggest this man is guilty.


“Might” is similar to “may” but the degree of possibility is even more uncertain .


  • Those girls might be watching us.
  • might not finish my career next semester.


It resembles “might” and translates to “could . ” On the other hand, the negative form (couldn’t) is not used to express probability but as a modal verb of ability and ability.


  • A lot of accident could be prevented.
  • This new vaccine could be an important step against Covid-19 fight.

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