In French, some of the most useful verbs are 'modal' verbs. They help express ideas like obligation, ability, or desire, and are usually followed by another verb in its infinitive form. We'll focus on four key ones: devoir, pouvoir, vouloir, and the expression il faut.

First, let's look at 'devoir'. It's used to express obligation or necessity, like 'must' or 'have to' in English. For example, 'Je dois partir' means 'I must leave'.

The present tense forms of 'devoir' are: je dois, tu dois, il ou elle doit, nous devons, vous devez, and ils ou elles doivent. Notice how they change for each subject.