How to use modal verbs for obligation & advice

What's the difference between internal and external obligation? What is a lack of obligation? And how to we express obligation or give advice using modal verbs in English? Find out in this video lesson...


Modal verbs are also very useful for expressing obligation and advice. So we'll look at a few example sentences together to help us understand how we use modal verbs to express obligation and advice. Firstly, obligation means something that you have to do, you have no choice, this is like a rule, a rule that you must follow and you can't break. Advice is an idea or a suggestion that someone gives you because they think it's a good idea and they think it will help you.

The most common context for obligation is probably school rules, so we'll use school rules as an example to help us understand obligation in English. The most common modal verb for expressing school rules or any rule is 'must'. So, for example..."You must wear a uniform" or "You mustn't forget your books". It's possible to replace 'must' with 'have to' - 'have to' sounds a bit more informal, but there is also a slight difference in meaning between 'must' and 'have to'. Take a look at this example: "I must do my homework". "I have to do my homework". The meaning is very similar and really if you use either one it's not a problem. But the difference is between internal and external obligation. So if you say "I must do my homework" this is what we call internal obligation. "I must do my homework" because I want to pass my exams. I don't want to fail, it's important to me. "I have to do my homework" - this is external obligation. This means that someone is telling me to do this. For example, my teacher or my parents. "I have to do my homework" because if I don't, I will be in trouble, they will be angry with me!

If you want to express a lack of obligation, which means that something is not necessary, it's your choice, we use 'don't have to'. So you could say "in the UK, pupils at school must wear a uniform, but in France, pupils don't have to wear a uniform". This means that there's no obligation. There's no past form of 'must' in English, so if you want to use the past form of 'must', we use 'had to'. So, "when I was at school we had to wear a uniform", but "I don't have to wear a uniform now" or in the negative, "I didn't have to play football every day at school" but I did it because I wanted to. It was my choice because I loved it.

If something is not an obligation but its advice, we use 'should' or 'ought to'. They both mean the same thing but 'should' is more commonly used today. So for example if you want to give your friend some helpful advice, you could say: "You should study more" or "You ought to study more". This means I think it's a good idea. You don't have to do it, it's your choice, but I'm giving you some advice that I think is helpful to you.

So, to sum up 'must' and 'have to' are used for obligation in the present, 'don't have to' is used for a lack of obligation, 'had to' is used for obligation in the past, 'didn't have to' is used for a lack of obligation in the past, and 'should' or 'ought to' is used for advice. Easy!

So, you should practise these modal verbs by putting your ideas in the comments below. Tell us about your school rules, past and present, and put them in the comments below. You don't have to, it's your choice, but I think you should!

OK, thanks for watching. Go back and watch the video again if you need to practise this more. I think you should, that would be a good idea, because the more you watch, the easier it is to remember. Like the video, share it with your friends and subscribe to my YouTube channel and go to where you can find courses to help you practise every aspect of your English. Keep practising and I'll see you in the next video lesson.