Grammar essentials: Introduction to modals

What are modal verbs?

Very simply put, a modal verb is a helping verb, also known as a type of auxiliary verb, that adds meaning to the main verb. Modals enable you to use a single main verb in different ways, or modes.

The 8 most common modals are:

1. can
2. should
3. may
4. might
5. must
6. have to
7. would
8. will

(There are others, such as ought to, that are not as commonly used.)

You use modals all the time. The sentences, "I study," and, "I should study," and "I will study," all have obviously different meanings. The difference is the modal verb.

But you may not know just how versatile modals are. So, let's get into it. How do you think about them? How do you use them?

First, let's see how much you know already.

Quiz

Look at the sentences below. What is the difference in meaning between a and b? [Answers are at the bottom of the page.]

1a. I didn’t need to go.	1b. I needn’t have gone.
2a. You must be very careful.	2b. You must be very careless.
3a. You shouldn’t have done that.	3b. A gift? You shouldn’t have!
4a. He could have told me.	4b. He could have told me!
5a. I would say that.	5b. You would say that!
6a. I can’t tell.	6b. I can’t tell.

Simple examples

Let's start simply. If you say, "I can dance," the main verb is dance, and the modal verb, can, adds the function of ability.

Compare this to the sentence, "I don't dance." Notice how dance is still the main verb, but the modal, don't, adds the idea of the negative.

So modals are not like regular verbs, but they accompany and attenuate regular verbs, like auxiliaries. But auxiliaries are used to form tenses, questions and negatives, whereas modals add different ideas, as we have seen with "I can dance" above. More below about this.

Simple mistakes

Modals are unlike regular verbs in that they do not decline or conjugate like regular verbs.

• Negatives: you can say, "I dance" and, "I don't dance", but while you can say, "I can dance", you cannot say, "I can don't dance". 
• Time: you can say I danced, but you cannot say I canned dance.
• Questions: some modals use an auxiliary, eg, "I have to go" changes to "Do I have to go?"; but some don't, eg, "I must go" changes to "Must I go?"
• Continuous form: there is no continuous form attached to the modal, eg, I am canning dance.
• Third person 's': the modal does not take the extra letter, eg, He cans dance.

So all these reasons mean that they can be confusing, both in meaning, function and formation.

Which modal does what?

A big problem is that often one modal has many uses. For instance, must can be used to express many things: 

• Certainty
  • You must be tired after your long journey.
• Obligation
  • You must pay tax.
• Orders
  • You must stop tapping your foot.
• A recommendation
  • You must see the new Batman movie!"
• An interrogative
  • Must you go so soon?

Therefore, you can see that a bad question to ask is, "how do I use must?" It's bad because there are too many possible answers. It is better to ask, "How do I express obligation?" This is a question of category.

So, let's look at the possible categories.

List of uses

Modals can be used to express the following ideas—you can call them modalities, or you can simply say functions or categories. 

Looking at the categories and trying to think of an example for yourself is a kind of "backward learning." You know the necessary modals (there are just 8 basic ones), but this analysis is a way of thinking about it you might not have done before.

Take a look at each one. How many ways can you think to express it?

• permission
• denial of permission
• obligation
• lack of obligation
• necessity
• lack of necessity
• possibility
• probability
• ability
• lack of ability
• capability
• positive assumption
• negative assumption
• advice
• prediction
• intention
• promise
• offer
• request
• suggestion
• criticism
• prohibition
• insist
• willingness
• habit 

If you don't know any modals that fit into an above category, then that means you need to study it! Book a lesson with a teacher and ask, for instance, "how do I express probability?" Alternatively, you can google that question.

With time and practice, you can master modals.

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Quiz Answers

1. a) I didn’t need to go. (I knew it was not necessary for me to go and for that reason, I did not go.) 
   b) I needn’t have gone. (I didn't know it was not necessary for me to go so I went.) 
2. a) You must be very careful. (I command you to be careful.)
   b) You must be very careless. (I conclude from the evidence that you are careless.)
3. a) You shouldn’t have done that. (I am criticising the fact that you did that.)   
   b) A gift? You shouldn’t have! (expression of surprise/gratitude at receiving an unexpected gift.)
4. a) He could have told me. (Maybe he told me but I am not sure.)
   b) He could have told me! (I am disappointed he didn't tell me although he had the opportunity or ability to do so.)
5. a) I would say that. (I agree.)
   b) You would say that! (It's typical of you to say that, and I disapprove somewhat.)
6. a) I can’t tell. (I do not have permission to give you that information.)
   b) I can’t tell. (I am unable to understand, or unable to differentiate between two things.)