Modal verbs are the verbs that express ability, permission, obligation, desire, and possibility. Dutch has six main modal verbs: kunnen (can/be able to), mogen (may/be allowed to), moeten (must/have to), willen (want to), zullen (shall/will), and hoeven (need to — used mainly in negatives: niet hoeven te). All of them combine with an infinitive at the end of the clause to express their meaning.
The sentence structure is: subject + modal (conjugated) + [rest of clause] + infinitive. “Ik kan Nederlands spreken” (I can speak Dutch). “Hij moet morgen werken” (He has to work tomorrow). “Wij willen naar Amsterdam gaan” (We want to go to Amsterdam). In subordinate clauses, both the modal and the infinitive cluster at the end: “…omdat ik Nederlands wil leren.” This double-verb cluster at the end is one of Dutch’s most distinctive grammatical features.
A crucial distinction: mogen (permission) vs. kunnen (ability). “Mag ik hier zitten?” (May I sit here? — asking permission) vs. “Kan ik hier zitten?” (Can I sit here? — asking if physically possible). In everyday speech the boundary blurs, but in formal contexts the distinction matters. Also note: moeten in the negative becomes niet hoeven te: “I don’t have to” is “Ik hoef niet te…” — not “Ik moet niet…” which means “I must not.”