What are modal verbs? How do they work in German?

In German there are six modal verbs - können, wollen, dürfen, müssen, sollen and mögen. They allow you to say what you can, want, may, must, should or like to do. They are used slightly differently to other German verbs, because they don't follow all the normal rules that other verbs do and especially because they are used with another verb. This second verb is in the infinitive - so it isn't changed at all - and goes to the end of the sentence. Any extra information in the sentence can go in the middle!
It's important to make sure you know how to form these verbs properly - but you probably already know them without realising, because you've seen them already in use as they are quite common. The main things to remember: the modal verb in the correct tense and form, and the other verb at the end in the infinitive.