Learning English

In this session we're looking at modals. They are words like can, could, may, might and must. We use them in lots of different ways.

We often use modals we're not sure about something. For example, when we think something is possible or true, but we don't have all the information.

It's quite hard to talk about modals without example sentences, so let's go straight in and read a story which uses lots of them.

Read the text and complete the activity

To do

Read this story. Pay attention to all the modals in it. Then you'll answer some questions to see how much you understand. After this we'll look at meaning and form in more detail.

Story

Mo loves space. He thinks there might be life forms on Mars. He says NASA found methane gas on the planet that may suggest this. He says scientists aren’t sure but it’s possible that it could be coming from very small bacteria-like organisms.

When he told his sister Jo, she said: "Oh, it can’t be true! Mars is a dead planet, isn’t it? There must be another explanation."

Mo replied: "Well their information might not be completely accurate. But a few years ago they found the remains of an ancient lake on Mars. NASA says it may have been suitable for life in the past. So who knows what’s there now?"

Summary – meaning and use

Might, may and could – used for what we think was possible in the present or past.

• There might / may/ could be life forms on Mars.
• NASA says it may / might / could have been suitable for life in the past.

Might not (mightn’t) and may not - used for talking about negative possibility in the present or past.

• Their information might not/may not be correct.
• They mightn’t have got correct data.

Couldn’t – used for something that is completely impossible.

• Other scientists say that there couldn’t be life on Mars.
• The gas couldn’t be coming from living organisms.

Must and can't – used for strong beliefs.

• Oh, it can’t be true! (I believe strongly that it isn’t true)
• There must be another explanation. (I believe there’s another explanation)
• They must have made a mistake! (I believe they have made a mistake)

Form

Present positive

The present positive is might / may / could / must + the infinitive of the verb be or another verb. Or the continuous be + verb-ing.

• The information might be correct.
• They must know that it isn’t possible.
• Bacteria-like organisms could be producing the gas.

Present negative

The present negative is might not / mightn’t / may not / can’t / couldn’t + the infinitive of the verb be or another verb. Or the continuous be + verb-ing.

• Their information may not be correct.
• They can’t have got the correct data.
• The gas couldn’t be coming from living organisms.

Past positive

The past positive is might / may / could / must + have + been or the past participle of another verb. Or the continuous been + verb-ing.

• There must have been water on Mars in the past.
• Something might have existed there.
• Who knows what could have been living in that lake?

Past negative

The past negative is might not / mightn’t / may not / can’t / couldn’t + have + been or the past participle of another verb. Or the continuous been + verb-ing.

• There may not have been anything in the lake.
• Scientists can’t have found anything definite.
• They mightn’t have been looking in the right area.

For more notes on modals, visit our grammar reference area.

Next

So, do you think you know how to use these modals? Next we're going to try them out by solving a murder mystery riddle. You're the detective - can you work out what happened?