Rules and Advice: Using "Must" and "Should" in the English Language

When using the English language, there are two important words you can use to either suggest something or say something is obligatory.

When you would like to make a suggestion (or give advice), you can use the word should, and its negative form shouldn't.

When you want to express that something is obligatory, imperative, or a rule, you can use the word must, and its negative form mustn't. Today we're going to look at how to form sentences using these words.

Should & Shouldn't

You can use "should" in the affirmative like this:

Subject + should + infinitive (without "to")

For example: "You should study before an exam."

In this case, the speaker is saying that they think it is a good idea to study before an exam.

You can also use it in the negative like this:

Even though it is really delicious...

Subject + shouldn't + infinitive (without "to")

For example: "You shouldn't eat lots of chocolate every day."

In this example, the speaker thinks that eating lots of chocolate every day is a bad idea. Don't eat lots of chocolate!

Must & Mustn't

Must and mustn't are used similarly to should and shouldn't, but are much stronger. Sentences are formed in exactly the same way.

Subject + must + infinitive (without "to")

For example: "You must have a driving licence to drive a car."

In this example, it is obligatory to have a driving licence.

The negative works in the same way:

Subject + mustn't + infinitive (without "to")

For example: "You mustn't drink and drive".

It is illegal to drink and drive. Therefore this is something you cannot do.

Questions

Both must and should form questions in the same way, too.

Must/Should + subject + infinitive (without "to")

If you are asking for advice, for example: "Should I go to the party?"

Or if you are asking about a rule or something obligatory: "Must I do my homework?"

And that's it! We hope our advice will help you when you need to give advice or orders in the English language!