I told my husband last night that I was starting a new English Grammar Pill series on modal verbs and his immediate response was: “What are modal verbs?!” Once I had got over the shock of realising that my husband is a complete English grammar ignoramus, I began to wonder whether my blog should also be directed at native speakers who have forgotten basic grammar rules. One thing it did prove, though, was how native speakers of any language, particularly English, have an instinctive feel of how to use their native language but are not necessarily able to explain areas of grammar. That’s for another post altogether.

I have had many requests from various learners to cover this tricky area of grammar, so I’ve decided that it would be a good idea to write about with this topic. Let me start with an introduction.


What are modal verbs?
Modal verbs are known as auxiliary (helper) verbs. They are used with other main verbs. The verb that follows is an infinitive without to.
Example: Sorry, I must go now. (NOT I must to go now)

The modal verbs are can, could, will, would, may, might, must, ought to, shall and should.

  • Two modal verbs cannot be put together.
  • They only have one form, so there is no -s in the third person singular and no form with -ing and -ed.

Questions are made by putting the modal in front of the subject (Can I…?, Should we….?) whilst negatives are made by putting not immediately after the modal (I cannot, I should not, He will not). The negatives can be contracted (I can’t, I shouldn’t, he won’t) in spoken English and informal written English.

What are their functions?
Modal verbs can be divided in the following functions:

  • Probability – when we want to say how sure we are that something happened / is happening / will happen. They are known as ‘modals of deduction’ or ‘speculation’ or ‘certainty’ or ‘probability’.
  • Abilityto talk about skills
  • Obligation (Necessity) to talk about things that are necessary or unnecessary
  • Adviceto give advice and make recommendations
  • Permissionto give or ask for permission
  • Habitsto talk about things we usually do or did in the past
  • Making requests or offers –  asking for something or offering to do something

There are too many functions to cover in one post, so I propose to split the functions into three posts.

In today’s post, I’d like to address the functions of ability (present and past) and habits and how to use them correctly.


Ability can refer to:
General ability – once you have learned something you can do it any time you want, like being able to read or swim or speak a language

Specific ability – something that you can or can’t do in one particular situation. For example, being able to repair something, or find something you are looking for.

Depending on what ability we’re referring to will determine what modal verb you use. The difference is more relevant for past ability rather than present ability,

Present Ability
We use can or can’t (cannot in formal writing) to talk about a skill and ability we either have or don’t have.

  • Can you deliver the parcels by Friday? No, I can’t.
  • I can’t speak German.
  • I can’t play the piano.
  • I can run 10km in 40 minutes.

We sometimes use be able to/unable to instead of can/cannot. This is common in writing.

  • They are able to deliver the goods next week.
  • I am unable to start my car.

When we talk about general past ability (not a specific ability) we use could/could not

  • In my twenties, I could play football very well.(but I cannot now)
  • Last year I couldn’t run 10k, but now I can run a half marathon!

If we talk about specific ability in the past we normally use was/were able to, managed to rather than could

  • I was able to/managed to install the new app onto my computer.
  • He managed to arrange the car hire for our holiday.

In questions and negative sentences we can use could, was/were able to, and managed to.

  • They couldn’t/weren’t able to hear the guide.
  • Could you/Were you able to/did you manage to talk to your boss today?
  • Sorry, I couldn’t/wasn’t able/didn’t manage to finish the sales report yesterday.

Click here if you’d like to try a modal verb of ability exercise prepared by Perfect English Grammar.

We can use will and would to talk about habits or things we usually do, or did in the past.

  • When I lived in the country, I would often go for long walks in the hills near my cottage.
  • Alison will always be late!

In the next post, I will cover modal verbs of obligation (necessity) and permission. In the meantime, please do not hesitate to ask me any questions you may have on this post.

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Ciao for now.


Business Grammar Builder, Paul Emmerson (Macmillan) 2010
Perfect English Grammar