Modal verbs: infinitive at the end
When you want to express ability, necessity, or desire in German, you will likely use a modal verb like können, müssen, or wollen. English speakers often trip over how these verbs interact with the rest of the sentence. Instead of keeping the two verbs right next to each other, German splits them up and sends the main verb to the absolute end of the clause.
In an ordinary main clause, the modal verb takes the second position in the sentence. It conjugates to match the subject, just like a regular verb. The main action verb is then pushed all the way to the end of the sentence.
Crucially, this final verb appears as an infinitive. It stays in its dictionary form without any extra words. English speakers frequently make the mistake of adding zu (the equivalent of English "to") before the final verb, but German modal verbs never take zu.
In English, you often need helper words like "do" or "does" to ask questions or make negative statements. German modal verbs do not use these helpers. To ask a question, simply move the conjugated modal verb to the front of the sentence. The bare infinitive remains securely at the end.
To make a sentence negative, just add nicht. Pay special attention to the verb dürfen. While it usually translates to "may" or "to be allowed to", adding a negative makes it the strict equivalent of the English "must not". Using müssen with a negative simply means you do not have to do something.
The verb mögen generally translates to "to like". You will often see it functioning as a main verb followed directly by a noun. However, it can also act as a modal verb paired with an infinitive at the end of the sentence. This is especially true for its highly common "would like" form, möchten.
You can also use the phrase lieber mögen to express that you prefer doing one activity over another. As always, the main verb stays at the end of the clause.
When using modal verbs in an ordinary main clause, put the conjugated modal verb in the second position and send the main verb to the very end of the sentence. The verb at the end is an infinitive, meaning you should never include zu before it.