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What Is Their Main Difference?
The main difference between modal verbs 'might' and 'must' is that 'might' talks about permission and 'must' talks about obligations.
Modal Verb Might
'Might' is a modal verb mainly used to show possibilities and to give advice. 'Might' is considered as the past tense of 'may' but it can be used in the present and the future tense. Take a look at the following example:
You
They
Modal Verb Must
'Must' is a modal verb that is mainly used to show that something is a necessity. It is also used to talk about likely events and suggestions. For example:
She
You
Similarities
Talking about Possibilities
'Might' and 'must' are used to show possibilities and probabilities. 'Must' talks about a great chance of occurrence, while 'might' talks about a lesser chance of occurrence. For instance:
He
He
Negation and Question
Modal verbs are used to make negative or interrogative sentences.
To make negative sentences, we add 'not' to the modal verb as illustrated below:
- Might → Might not → Mightn't
- Must → Must not → Mustn't
Look at the examples below to see the negation process:
I
I
To create interrogative form, we invert the modal verb with the subject:
They
He
With Other Modals
We use only one modal verb in a sentence. We cannot use modal verbs with other modal verbs. Take a look at these incorrect sentences:
I
I
Differences
Talking about Necessities
We use 'must' to talk about actions or events that need to be done. The occurrence of these events is a necessity and at times a duty. For instance:
You
All citizens
Giving Advice
We often use 'might' to politely give advice or a fair warning. In this case, we often pair 'might' with 'want' as the main verb. Take a look at the following examples:
You
You
Giving Suggestions
'Might' is used to make a suggestion about a future possibility. For instance:
You
You
With Conditionals
'May' and 'must' can be used as conditional verbs. In the table below, you can see an overview of 'might' and 'must' with all conditional types:
| Might | Must | |
|---|---|---|
| Conditional Type 1 | ✓ | ✓ |
| Conditional Type 2 | ✓ | ✗ |
| Conditional Type 3 | ✓ | ✗ |
| Zero Conditional | ✗ | ✗ |
Conditional Type 1
'Might' and 'must' are used in conditional type 1. In this type, we show a condition and its results. These conditions are real situations with a high chance of occurrence. For instance:
If you run everyday, you
If you run everyday, you
Conditional Type 2
This type of conditionals is used to talk about hypothetical situations in the present or future. These situations are imaginary and they have a low chance of occurrence. We use 'might' in this conditional. We cannot use 'must' in this type since it indicates certainty which cannot be applied to hypothetical situations. Take a look at the following example:
If I take a couple of weeks off, I
If I finish this task, I
Conditional Type 3
Conditional type 3 talks about an imaginary past that could happen but never did. We often use it to express lost causes and what-ifs. We use 'might' in this type of conditional. 'Must' cannot be used in this conditional. For example:
You
I
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