Modal Verbs: Can, Could, Should— A2 Grammar Exercises

A child asks: Can I have some water? Looking at an old photo, you say: I could run so fast when I was ten. A doctor tells you: You should drink more water. These three sentences use three different modal verbs: can, could, and should. Each one does a specific job.

Modal verbs sit before the main verb and change its meaning. They show ability, possibility, permission, or advice. They're short, frequent, and follow special grammar rules that are different from normal verbs.

Form: how modals work

All three modals follow the same simple pattern. The modal is the same for every subject: no -s for he, she, or it. After the modal, you use the base form of the verb: no to, no -ing, no -ed.

Negative short forms

• can not → can't (also written as one word: cannot)
• could not → couldn't
• should not → shouldn't

The short forms are much more common than the full forms in everyday English.

Can

1. Ability: what you know how to do

The most basic use of can: skills and abilities you have right now.

• I can swim, but I can't dive.
• My grandfather can read Latin.
• Penguins can't fly, but they can swim very well.
• Can you drive a motorbike?

2. Permission: what's allowed

Use can to ask for or give permission. It's the everyday word for this.

• You can use my phone if you need to.
• Children can't enter the bar without an adult.
• Can I leave early today?
• Sorry, you can't park here.

3. Requests: asking someone to do something

Use Can you…? to ask someone for help. It's friendly and common between people who know each other.

• Can you help me with this bag?
• Can you repeat the question, please?
• Can you send me the link?
• Can you wait a moment? I need to find my keys.

4. Possibility: what's possible in general

Can describes what is possible in general: things that happen sometimes, or things that are true in certain conditions.

• Winter can be very cold here.
• Cats can live for 20 years.
• This medicine can cause headaches.

Could

Could is the past form of can, but it also has its own present-time jobs. Both uses are common.

1. Past ability: what you could do before

Use could for general abilities you had in the past: skills, talents, things that were true over a period of time.

• I could read when I was four.
• My grandmother could speak five languages.
• When I was younger, I could run a marathon.
• She couldn't ride a bike until she was twelve.

And one important point: for present ability, use can, not could. I could swim means in the past. To say you can swim now, you have to say I can swim.

2. Polite requests: softer than can

Use Could you…? to ask for help in a more polite way. It's the standard form for strangers, formal situations, or when you want to sound less direct.

3. Possibility: things that might happen

Use could for things that are possible but not certain. It's softer than will; you're saying "maybe", not "definitely". The difference from can for possibility is important: can describes what's generally possible in the world (things that are sometimes true), while could describes what might happen in a specific situation. Compare: Winter can be cold here (general truth, every year) vs It could be cold tomorrow (specific prediction about one day).

• It could rain later; take an umbrella.
• This could be a problem.
• You could try the new café on Park Street.

Should

1. Advice: what's a good idea

Use should when you think something is a good idea, or when you give advice. It's not as strong as must: you're recommending, not ordering.

• You should drink more water.
• You look tired. You should go to bed early.
• Tom should call his mother more often.
• You shouldn't eat so much sugar.
• We shouldn't be late; the train leaves at 8.
• I think you should apologise to her.

2. Asking for advice

Use Should I…? or What should I…? when you want someone's opinion or recommendation.

• Should I call the doctor?
• What should we do this weekend?
• Where should I put the keys?

Common mistakes

The "no to" rule from mistake 2 applies to could and should in exactly the same way: She could read at four (not could to read), You should study more (not should to study). The rule never changes between modals.

Can vs could for requests

Both ask someone to do something. The difference is how polite or formal you sound.

Quick comparison: the three modals at a glance

Quick summary

Related topics

• Must and have to: for stronger obligations and rules.
• May and might: for more formal permission and possibility.
• Imperative: another way to give instructions or suggestions.