Modal verbs

This lesson has two parts. Part 1 explains the grammar of modal verbs and where they are placed in a sentence or question. Part 2 explains the meaning of each modal verb and provides example sentences.

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Modal verbs are also called modal auxiliary verbs, modal auxiliaries, or simply modals. These verbs are a subcategory of auxiliary verbs, which means they cannot be used without a main verb. English has ten modal verbs.

can   could
may might
shall should
will would
must ought

While the meaning and usage of modal verbs is complicated, the grammar is simple. Modal verbs are not conjugated: they have no tense and no person, so they never change.

All modal verbs must be followed by a main verb in the base form except for ought which is followed by an infinitive.

subject modal
verb
main verb
(base form)
 
They can come  
Mike should walk.  
You must go  
We will wait.  
She ought study. incorrect

Attention: many English learners make the mistake of placing an infinitive after every modal verb. This is incorrect.

subject modal
verb
main verb
(infinitive)
 
They can to come. incorrect
Mike should to walk. incorrect
You must to go. incorrect
We will to wait. incorrect
She ought to study.  

In statements, the word order is subject + modal + main verb.

subject modal
verb
main
verb
 
Tom and Sue might arrive later.
Everyone can swim.  

In questions, the word order changes to modal + subject + main verb. Here are some examples with Yes / No questions.

modal
verb
subject main
verb
Can they come?
Should Mike drive?

Here are some examples with Wh- questions.

Wh- word modal
verb
subject main
verb
When can they eat?
How could he walk?

When forming negative statements, the negative adverb not is placed between the modal verb and the main verb.

subject modal
verb
  main
verb
 
You must not disturb the baby.
They should not drive at night.

When asking questions in the negative, the modal verb and a negative adverb not are always contractions.

modal + not
(contracted)
subject main
verb
 
Couldn’t Tom come to the party?
Shouldn’t you rest?  

To learn more details about modal verbs and how they express moods such as ability, possibility, necessity or other conditions, go to page 2.

 
Related lessons:

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