Six modals, one pattern: ich = er, infinitive at the end.

German has six modal verbs: können (can / be able to), müssen (must / have to), dürfen (may / be allowed to), sollen (should / be supposed to), wollen (want to), and mögen (like). A seventh form, möchten ("would like to"), is technically the Konjunktiv II of mögen but functions as its own present-tense modal in everyday speech. Modal verbs bend the meaning of another verb in the sentence and are introduced in the first weeks of every A1 curriculum.

Modal verbs share an irregular pattern: the ich and er/sie/es forms are identical and use a vowel-changed stem — ich kann / er kann, ich muss / er muss, ich darf / er darf, ich will / er will, ich mag / er mag. Only sollen keeps its original stem unchanged (ich soll / er soll). The plural forms wir, sie, and Sie use the infinitive stem with standard -en endings; ihr uses -t with the original stem. This 1st = 3rd singular collision is the defining signature of German modal conjugation.

Both translate loosely as "must" or "should" in English, which is the single biggest source of confusion. Müssen expresses internal or objective necessity — the pressure comes from the situation itself: "Ich muss um fünf gehen" (I have to leave by five). Sollen expresses external instruction or expectation from another person: "Du sollst ihn anrufen" (You are supposed to call him — someone else told you to). The English "should" maps to sollen when reporting an external expectation, and to sollte (Konjunktiv II of sollen) when giving advice.

Dürfen expresses permission — whether one is allowed to do something: "Darf ich hier rauchen?" (Am I allowed to smoke here?). Können expresses ability or possibility — whether one is capable of doing something: "Ich kann schwimmen" (I can swim). In English both collapse onto "can," so learners often reach for können when permission is actually meant. In formal German, "Kann ich hier rauchen?" asking for permission is considered a mistake; "Darf ich?" is the correct form.

Mögen (ich mag) expresses a general liking or preference, most often with a noun object: "Ich mag Kaffee" (I like coffee). Möchten (ich möchte) means "would like to" and is used for polite requests, most often with an infinitive or a noun in an ordering context: "Ich möchte einen Kaffee" (I would like a coffee). Möchten is grammatically the Konjunktiv II of mögen, but in everyday speech it functions as a standalone present-tense modal. Use mögen for stating general preferences and möchten when placing an order, making a request, or expressing a current desire.

The second verb goes to the very end of the clause in its bare infinitive form, creating the Satzklammer ("verb bracket"): the conjugated modal sits in position 2, the infinitive closes the clause. Example: "Ich kann morgen Deutsch lernen." In a subordinate clause introduced by weil, dass, or wenn, the modal itself moves to the end and the infinitive comes just before it: "…weil ich morgen Deutsch lernen kann." This verb-bracket pattern is the same structure used by separable verbs and the Perfekt tense.

Modal verbs overwhelmingly use Präteritum, not Perfekt, even in spoken German — just like sein, haben, and werden. The six Präteritum forms are: konnte (could), musste (had to), durfte (was allowed to), sollte (was supposed to), wollte (wanted to), mochte (liked). All six follow the regular weak-verb -te- pattern. The vowel-changed singular stems (kann-, muss-, darf-, mag-) revert to their root forms (konn-, muss-, durf-, moch-) in the past. Saying "ich konnte" in conversation is perfectly natural; "ich habe gekonnt" as a simple past sounds markedly odd.

When a modal appears in the Perfekt (or Plusquamperfekt or Futur II) together with another infinitive, the modal's Partizip II is replaced by its infinitive form — producing two infinitives at the end of the clause: "Ich habe arbeiten müssen" (I had to work), not "Ich habe arbeiten gemusst." The auxiliary is always haben, never sein, even when the secondary infinitive would normally take sein. If the modal stands alone with no secondary infinitive, the standard Partizip II is used: "Ich habe es gekonnt" (I managed it).