Modal Verb Basics - Explanation

Modal verbs can be confusing for many students. This quick guide and follow-up quizzes will help you understand the basics of modal verbs. After studying the following chart, try the challenging modal verb quizzes listed at the bottom of this page.

Ability

Can do something / Able to do something 

Someone has an ability to do something.

Peter can speak French.
Anna is able to play the violin..

Possibility  

Could do something/ Might do something / May do something / Can do something

It's possible for someone to do something.

Peter could help you this afternoon.
Alice might have gone to the bank.
They may know the answers. 
She can come to the party next week. 

Obligation

Have to do something

It's a daily requirement of a job or some other common task.

Peter has to help customers at the store.
They have to get up early on Saturdays.

Need to do something

It's important to do something.

I need to get some milk and eggs for dinner.
She needs to do her homework tonight.

Must do something

It's personally important for someone to do something.

I must leave soon because the train leaves in one hour.
I must study if I want to get an A.

Prohibition

Mustn't do something

It's forbidden for someone to do something.

Children mustn't go into this room.
Motorcycles mustn't be ridden on this road. 

Non-necessity 

Don't have to do something / Don't need to do something

It isn't necessary for someone to do something, but it is also possible.

You don't have to take this class, but it's interesting.
You don't need to get up early on Saturday.
She doesn't have to work on Sundays, but she does sometimes.
Mary doesn't need worry about the wash. I'll take care of it. 

Advisability 

Should do something / Ought to do something / Had better do something

It's a good idea for someone to do something. It's someone's suggestion to someone.

You ought to see a doctor.
Jennifer should study harder.
Peter had better hurry up.

Shouldn't do something

It isn't a good idea for someone to do something.

You shouldn't work so hard.
They shouldn't ask questions during the presentation. 

Certainty

Modal verbs can also be used to show how probable something is. These are known as modal verbs of probability and follow similar patterns in the present and the past. 

must be 

The speaker is 90% sure the sentence is true. 

She must be happy today. She's got a huge smile on her face.
Tom must be in a meeting. He's not answering his phone. 

could be / might be / may be

The speaker is 50% sure the sentence is true. 

They could be at the party.
She might be happy if you give her the present.
They may be angry with their parents.

can't be / mustn't be / couldn't be

The speaker is 90% sure that something is not true.

You can't be serious.
They mustn't be the ones we ordered.
She couldn't be at the party. 

might not be / may not be

The speaker is 50% sure that something is not true.

They might not be in agreement on this contract.
Tom may not be at school. 

Now, try the quizzes:

Modal Verb Review Quiz 1