How to use modal verbs

What are modal verbs exactly? They are a subset of auxiliary verbs typically used to express modality e.g. properties such as obligation, possibility etc.

What are the main modal verbs?

  • can and could
  • may and might
  • shall and should
  • will and would

Modal verbs in English work in a slightly different way to main verbs but they function as auxiliary verbs, i.e. they modify the modality of another verb, which they govern. For example:

  • They don’t change in the 3rd person form
  • There is no past tense of a modal verb, you have to add an auxiliary and a past participle
  • There is no infinitive form

Here are the different uses of modals:

  • Obligation / necessity – e.g. I must remember to phone my mum tonight or You have to wear a seatbelt in the car
  • Advice or opinion – e.g. You should go see a doctor if you are sick or I think the government should change their policy on health
  • Deduction – e.g. They must be out, there aren’t any lights on, She’s not at home. She may be working or He can’t be ill. I saw him running in the park
  • Ability and possibility – e.g. I can speak Italian very well, They couldn’t wait because they were in a hurry or They weren’t able to come

In the past modal verbs take this form:
Subject + modal verb + have + past participle – e.g. He’s late, he must have overslept!

There are some other verbs too which mostly share the same features as the main modal verbs but there are certain difference:

  • ought – differs from the main modals as you have to add ‘to’ after it, e.g. compare: he should go or he ought to go
  • dare and need – they be used as modal verbs often in the negative, e.g. You dare not do that or You need not go
  • had better – behaves like a modal verb but it is considered a compound verb but can be classes as a modal
  • used to – can behave like a modal but is often used with ‘do’ to support it, e.g. Did she use to do it? or she didn’t use to do it

Modal verbs are always useful in English, we also did a podcast episode on them. We hope it gives you a much better idea of how to use them: