Number one for English language teachers

Grammar: teaching the modals 'ought to', 'should', 'must' and 'have to'.

Level: Starter/beginner, Elementary, Pre-intermediate, Intermediate, Upper intermediate, Advanced Type: Reference material, Teaching notes

Suggestions for teaching the modals 'ought to', 'should', 'must' and 'have to' when talking about suggestion or advice.


I have recently started teaching English in the sultanate of Oman. Please give me some ideas on how to teach the modal verbs ‘ought to’, ‘should’, ‘must’ and ‘have to’. I don’t find these easy and am having great difficulty in planning a teaching lesson.
How do I teach ‘should’ and ‘shouldn’t’ to indicate suggestion/advice?

Joanna West

Modal verbs present specific problems for both teachers and learners. Quite apart from the numerous difficulties associated with meaning, their use also differs from other verbs in a number of ways, notably:

  1. Forming the interrogative through inversion rather than the use of the auxiliary verb ‘do’ (so ‘Can I?’ rather than *‘Do I can?’)
  2. Forming the negative by adding ‘not’ to the modal verb rather than using the auxiliary verb ‘do’ (‘You mustn’t’ and not *‘You don’t must’)
  3. No –s ending in the third person singular
  4. No consistent past forms in some cases.
  5. ‘Have to’, however, is different, forming interrogatives and negatives using ‘do’ and having a ‘normal’ past form.

In terms of teaching the modal verbs, the list of verbs in the first question suggests that the distinction between ‘ought to’ and ‘should’ and ‘must’ and ‘have to’ respectively is the key point, which also suggests that the learners in question have reached a fair degree of proficiency in English.


1) Must and have to

A key distinction between ‘must’ and ‘have to’ can be found in the negative forms. Whereas ‘You must go’ and ‘You have to go’ can be regarded as broadly the same in terms of meaning, ‘You mustn’t go’ and ‘You don’t have to go’ are quite different, the first indicating that going is prohibited in some way, or even dangerous, while the second implies an absence of obligation or need.

Another difference between ‘must’ and ‘have to’ in the sense of obligation can be found in the nature of the obligation. It is possible to say ‘I’m sorry. I can’t come to the meeting tomorrow because I have to go to the dentist at 3 o’clock’ but not ‘I can’t come to the meeting tomorrow because I must go the dentist at 3 o’clock’. On the other hand, if you have a raging toothache, you would probably say ‘I really must go to the dentist’, although ‘have to’ could replace ‘must’ in this sentence. A generalized distinction would be that ‘must’ refers to an internal need or obligation while ‘have to’ is used to refer to an external need or obligation. It is probably true to say, however, that ‘must’ can generally be replaced by ‘have to’ but ‘have to’ often cannot be replaced by ‘must’ so in terms of teaching, it is probably a good idea to teach ‘have to’ for obligation because it is nearly always correct whereas ‘must’ is often inappropriate. ‘Must’ and ‘must not’ are useful for official notices and instructions, e.g. ‘You must carry your passport at all times’ and ‘You must not smoke in the toilets’.


2) Should and ought to

‘Should’ and ‘ought to’ are basically the same, although ‘should’ is much more widely used than ‘ought to’. The negative and interrogative forms of ‘ought to’ are becoming increasingly rare. Both ‘should’ and ‘ought to’ are used to talk about obligation and duty and to give advice. One way of getting the meaning of ‘should’ across to learners is to contrast its meaning with that of ‘must’ and ‘have to’ as the degree of obligation is considerably less, e.g. ‘I have to go to the doctor’ as compared to ‘I should go to the doctor’.

It is probably a good idea to practise the above verbs using a generative context, i.e a simple context that can generate lots of examples. In the case of ‘should’ and ‘shouldn’t’, you might ask your learners to think of things they should and should do if they want to improve their English. Answers might include ‘You should read a lot in English’, ‘You should learn vocabulary in context’, ‘You should talk to English people’, ‘You shouldn’t talk Arabic in class’ and ‘You shouldn’t translate everything’. Other simple contexts where you give advice might include how to lose weight, what to do if you have a bad cold, how to give up smoking, how to be successful at an interview and so on.

At higher levels, it is more appropriate to contrast different modal verbs and to concentrate on nuances of meaning. At lower levels it is probably best to concentrate on the main meaning of each modal verb rather than to confuse learners by introducing too many meanings at once. In the case of ‘must’, for example, its use for expressing deduction or concluding that something is certain, as in ‘The keys must be on the kitchen table’, is a useful one but is arguably confusing for learners at lower levels, particularly as the negative form is ‘can’t’ and ‘not ‘mustn’t’.

Many coursebooks introduce the most important modal verbs first and concentrate on their main meanings initially. Make full use of the way coursebooks present and practise the key modal verbs. You don’t need to reinvent the wheel. Contrasting some of the verbs (e.g. ‘have to’ and ‘should’) can help to consolidate the meaning and giving plenty of relevant practice in generative situations should help your learners to understand and use these verbs correctly.

Back to Ask the experts Grammar in Ask the experts

Rate this resource (4.14 average user rating)

  • 1 star out of 5
  • 2 stars out of 5
  • 3 stars out of 5
  • 4 stars out of 5
  • 5 stars out of 5

You must be signed in to rate.

  • Share

Readers' comments (8)

  • What Andyn says about 'must' absolutely correct. Very easy to double-check going through the 50 free sample sentences in the BNC. The British National Corpus. I once did it before teaching a lesson incorporating 'must' and was mildly shocked by my own 'discovery'.

    Unsuitable or offensive? Report this comment

  • Very nice and clear explanation and very good to use in class.

    Unsuitable or offensive? Report this comment

  • I have used 'Agony Aunt' letters from magazines but without the advice which has resulted in some lively discussions. For one on one I have both given instructions on how to play backgammon and received instructions on how to play chess.

    Unsuitable or offensive? Report this comment

  • Recent research into corpus (both spoken and written) has revealed that 'must' used for deduction/speculation is far more commonly used than 'must' for obligation and perhaps we should reconsider at which stage it should be taught.

    Unsuitable or offensive? Report this comment

  • Modal auxiliaries are a real wealth of the English language.
    They should be taught gradually, to avoid misleading the learners.

    I've really taken profit from this explanation.

    Thank you so much!

    Unsuitable or offensive? Report this comment

  • Sorry I wanted to rate it with 5 stars, but I think I pushed the wrong button... oops !

    Unsuitable or offensive? Report this comment

  • I know this is an old post, but for future reference, the difference between 'should' and 'ought to' as I know it is basically the level of emphasis you give to the 'advice' or 'obligation' being uttered.
    Ex. You should tell someone.
    You really should (ought to) tell someone.

    Unsuitable or offensive? Report this comment

  • This is a nice piece Tim.
    I might add an idea for freer practice
    agony aunt / student advisor scenario role play with invented problems.
    Eg. I have a rash, I have seen an unattended bag. I don't like my gift.

    Unsuitable or offensive? Report this comment

Have your say

You must sign in to make a comment

sign in register

Powered by Webstructure.NET