Modal verbs

Modal verbs sit in front of another verb and change what the sentence is doing: an ability, an obligation, a wish, a permission. They are among the most common verbs in German and they behave unlike anything else.

Two things happen when you use one:

1. The modal takes the normal verb position, second in the sentence.
2. The real verb goes to the very end, as an infinitive.

Ich kann heute nicht arbeiten. — I cannot work today.

English puts "work" in the middle. German holds it back to the end, and building that habit is most of the work here.

The six

The irregular part

Every modal has a shortened, irregular singular: ich and er/sie/es have no personal ending, and several modals also change their vowel. The plural returns to forms that look much closer to the infinitive. This contrast is the part to learn.

ich and er/sie/es are identical — no -t on the third person. That holds for all six, and it is the most common mistake beginners make with them.

sollen is the odd one out: no vowel change at all. ich soll, du sollst, er soll.

möchten, the one that is not quite a verb

möchten means "would like" and is how you ask for things politely. Technically it is a form of mögen; everybody treats it as its own verb because that is how it is used.

Ich möchte einen Kaffee, bitte. — I would like a coffee, please.

Use möchten to order and request — there ich will lands harder than "I want" does in English. For plans and intentions wollen is neutral: Ich will Deutsch lernen.

nicht müssen is the trap

nicht müssen does not mean must not. It means do not have to.

Du musst nicht kommen. — You do not have to come.

To say must not, use nicht dürfen:

Du darfst nicht kommen. — You are not allowed to come.

This one reverses the meaning of a sentence, and it is worth checking twice.

In the past

All six form their past with the simple past rather than the perfect, even in speech — like sein, haben, werden and wissen, they are exceptions to the "speak in the Perfekt" rule. The infinitive's umlaut disappears and -te is added: können → konnte; mögen also turns g into ch: mochte.

Ich konnte gestern nicht kommen. — I could not come yesterday.

More on which past tense to use in Perfekt or Präteritum.

What to actually memorise

The singular vowel changes, and the nicht müssen against nicht dürfen distinction. The word order looks after itself once you have said a few sentences aloud — the verb arriving at the end starts to feel natural faster than you expect.