Mini-Lesson Monday, Lesson #194 (Part 1): ‘Must’, ‘Have To/Have Got To, ‘Should’, And ‘Ought To’: Modal Verb Forms That Express Obligation

📗 ‘You must go back with me to the autumn of 1827.’

– Anne Brontë, The Tenant of Wildfell Hall

Since modal verbs (also known as auxiliary or helping verbs) are so important in English, we are going to look at four forms that are sometimes problematic for English learners of all levels. These are ‘must’, ‘have to’/ ‘have got to’, ‘should’, and ‘ought to’. To make things even more complicated, they can sometimes have different meanings when used negatively!

All of them are used to express obligation to an extent, but there are subtle (slight) differences between how we use them in English, which we will cover here.

I had been planning this Lesson for some days, and the book that came to mind for having many instances of modal verb forms of obligation was Anne Bronte’s The Tenant of Wildfell Hall (1848). I am including a short summary of it in the paragraph below (with spoilers, so don’t read it if you would like to read the classic for yourself!)

📜 It is the story of a woman who marries young, only to discover late that her husband is abusive and an alcoholic. After many years of trying to make her marriage work, she finally runs away with her infant son to a country cottage far enough away for her husband not to find her. Although the village folk are very curious and even suspicious of what has brought her to their village, she gradually earns their respect through the quiet and helpful life she leads. It seems that everything is set for her to enjoy a new life, when she hears that her husband is seriously ill, and her conscience urges her to return once more …

It so happened that a copy of the book, which I had ordered some weeks ago, arrived this afternoon – confirming that today was indeed the right day to talk about modal forms of obligation in The Tenant of Wildfell Hall. 😊

In Part 1 of this Lesson we will look at ‘must’, ‘have to’, and ‘have got to’. In Part 2 of this Lesson we will consider ‘should’ and ‘ought to’, and conclude with a comparative overview of all of these words together.


📗 ‘You must go back with me to the autumn of 1827.’

– Anne Brontë, The Tenant of Wildfell Hall

‘Must’, ‘have to’, and ‘have got to’ – these all speak of a sense of obligation.

The differences between them however are nuanced.


📝 ‘MUST’

✍️ ‘Must’ speaks of an internal, personal obligation or necessity. For example,

‘I must remember to drink more water’,

‘You must be motivated to study English full-time’, or,

‘I must answer that email soon’.

💡 In these sentences, the person who ‘must do something’ decides that something is necessary and assumes personal responsibility in the matter.

📗 “Arthur, you must repent!” cried I, in a frenzy of desperation, throwing my arms around him and burying my face in his bosom. “You shall say you are sorry for what you have done!”

– Anne Brontë, The Tenant of Wildfell Hall

📗 “No, I think not,” observed Rose; “for she didn’t seem very disconsolate after all; and she’s excessively pretty— handsome rather— you must see her, Gilbert; you will call her a perfect beauty, though you could hardly pretend to discover a resemblance between her and Eliza Millward.”

– Anne Brontë, The Tenant of Wildfell Hall (emphasis mine)

‘Must’ can also refer to probability or certainty. Here is an example from Anne Bronte’s novel:

📗 “Now shut the door, and come to the fire, while Rose gets the tea ready; I’m sure you must be starved;— and tell me what you’ve been about all day;— I like to know what my children have been about.”

– Anne Brontë, The Tenant of Wildfell Hall (probability or certainty – both could apply here)

📗 “Then, sir, I fear you must be very much worse than you should be …”

– Anne Brontë, The Tenant of Wildfell Hall (probability)

📗 You must be aware that your continuance here is excessively disagreeable to me—”

– Anne Brontë, The Tenant of Wildfell Hall (certainty)



✍️ ‘Have to’ and ‘have got to’ refer to an external, situational obligation. Here are some examples:

‘You have to register for the course in advance’,

‘He has to exercise more if he wants to lose weight’, or,

‘She has got to study harder if she wants to pass that exam.’

💡 In these examples, there is an external ‘force’ obliging someone else to act in a certain way, at a particular time. The obligation comes from another person or even the situation itself, not from the person who needs to do the action.

📗 “You will have to pay a higher price than you anticipate, if you don’t take care: there will be the total loss of your own health, and of my affection too, if that is of any value to you.”

– Anne Brontë, The Tenant of Wildfell (emphasis mine)

📗 “Either I should have to acknowledge the deed, which would set me down as a madman, unless I acknowledged the motive too— and that seemed impossible— or I must get up a lie, which seemed equally out of the question—”

– Anne Brontë, The Tenant of Wildfell (emphasis mine)

This distinction between ‘must’ on the one hand and ‘have to’/‘have got to’ is noticeable even in question format: you can compare the internal and external obligations respectively that are reflected in each quotation here:

📗 “She would love you with all her heart, if you deserved it.”

“What must I do to deserve it?”

– Anne Brontë, The Tenant of Wildfell Hall

📗 “Have I not proven to you how wrong it is— how contrary to Scripture and to reason, to teach a child to look with contempt and disgust upon the blessings of Providence, instead of to use them aright?”

– Anne Brontë, The Tenant of Wildfell Hall



‘Must’, ‘have got to’, and ‘have to’ are used in the present tense. The past tense for all three forms is ‘had to’. The future tense of all three forms is ‘will have to’.

📗 ‘He was never willing to go, and I frequently had to carry him away by force, for which he thought me very cruel and unjust; and sometimes his father would insist upon my letting him remain; and then I would leave him to his kind friends, and retire to indulge my bitterness and despair alone, or to rack my brains for a remedy to this great evil.’

– Anne Brontë, The Tenant of Wildfell Hall (emphasis mine)

📗 “You will have to pay a higher price than you anticipate, if you don’t take care: there will be the total loss of your own health, and of my affection too, if that is of any value to you.”

– Anne Brontë, The Tenant of Wildfell Hall (emphasis mine)



✍️ When ‘must not’ is used in a sentence, it means that there is a kind of negative obligation – you are not to do [something] – it is forbidden.

For example, when a visitor offers to help wash up the dishes after dinner, we tell them, ‘no thank you, you mustn’t think of washing up – you are our guest!’

✍️ But when we say ‘do not have to / don’t have to’ or ‘haven’t got to’ (the established negative forms of ‘have to’ or ‘have got to’), we mean there is no obligation at all – you do not need to do [something] – it is unnecessary.

So if I were to tell a visitor, ‘you don’t have to wash the dishes’, I am telling them that the choice is theirs: they don’t really have to wash the dishes, but they can if they want to. This is very different from using ‘must not’ in the same sentence!

📗 “If you would have your son to walk honourably through the world, you must not attempt to clear the stones from his path, but teach him to walk firmly over them— not insist upon leading him by the hand, but let him learn to go alone.”

– Anne Bronte, The Tenant of Wildfell Hall (emphasis mine)

👉 Note: However, when speaking about some strong negative obligation, it is more common to use ‘can’t’ or ‘cannot’ in spoken English than ‘must not’. E.g., ‘You cannot bring food or drinks into the library.’



Native English speakers tend to use ‘have to’/ ‘have got to’ more in spoken or informal English, whereas ‘must’ is the expected form in formal and written English.

✍️ ‘Must’ tends to sound more definitive too, which is why it is often used in regulations: ‘you must not walk on the grass’ or ‘you must have ID to purchase alcohol here’.

👉 That said however, we do use ‘must’ in spoken English when we want to express probability or certainty. You will here sentences like, ‘you must be tired’, ‘I must be mistaken’, ‘you must try this’, ‘we must have misunderstood’, or ‘she must be devastated’.

We have covered so much here – what a lot to reflect on! But there is more to come, so join me in Part 2 of this Lesson where we will look at ‘should’ and ‘ought to’, and then summarise the differences between these four modal verb forms together.

by J. E. Gibbons

English language tutor and researcher at 'Learn English Through Literature' (2024)