What are modal verbs?

Modal verbs, also called modal auxiliaries (in German: Modalverben), are verbs that modify the relationship between subject and predicate and, thus, determine the grammatical mood. In the vast majority of cases, they cannot stand alone (as the only verb) in a sentence and form a multi-part predicate together with the respective main verb. Note that this main verb must be in its infinitive (unconjugated) form and that no ‘zu’ (to) is used. Furthermore, it is neither possible to construct the passive voice nor an imperative with modals. Compare in detail:

• The German language knows the following six modal verbs:
  • können (can), wollen (want/would), sollen (should), mögen (want), dürfen (be allowed to), müssen (must)
• In a sentence, modal verbs appear as follows combined with the infinitive of the present full verb. The preposition ‘zu’ is not utilized with modals although it is typical for other occurrences of infinitives:
  • „Marius kann sehr gut Gitarre spielen.“ (Marius can play the guitar very well.)
    • ability
  • „Petra soll heute noch zurückrufen.“ (Petra is supposed to call back today.)
    • request/necessity/need
  • „Darf ich Sie was fragen?“ (May I ask you something?)
    • permission
  • „Hunde müssen draußen bleiben.“ (Dogs must stay outside.)
    • necessity
  • „Ich will den Film schon noch sehen.“ (I still want to see the film.)
    • wish
  • „Magst du mein Risotto probieren?“ (Would you like to try my risotto?)
    • concession/possibility

Using modal verbs as main verbs

In contrast to the general rule of usage, it is sometimes possible for modal verbs to appear without the infinitive of a full verb – that means as the only verb in a sentence. Here, there are two possibilities, although the distinction between the role as the main verb and elliptical use is not always clear. Note that English grammar does not offer such a possibility of using modal verbs in this way:

1. These example sentences show the modal verb functioning as the full verb:
   • „Meine Mutter will, dass ich um 12 Uhr zu Hause bin.“ (My mother wants me to be home by noon.)
     • The modal ‘will’ is the only verb in the clause.
   • „Peter kann sehr gut Englisch.“ (Peter speaks English very well.)
     • He has the ability to speak very good English. The modal ‘kann’ is sufficient to express that here.
   • „Wir alle mögen unsere neue Kollegin.“ (We all like our new colleague.)
     • Similarly, ‘mögen’ does not need an additional main verb here.
2. The following instances show how modals may occur with an ellipsis:
   • „Wir wollen am Wochenende in die Berge [fahren].“ (We want to go to the mountains this weekend.)
     • Mind the difference between the German and English sentence with and without ‘fahren’ (go).
   • „Möchtest du noch ein Stück Kuchen [haben]?“ (Would you like [to have] another piece of cake?)
   • „Was soll das Gehabe [bedeuten/sein/darstellen]?“ (What’s this behaviour [supposed to mean]?)

Further explanations related to ‘Modal verbs’

The following explanations refer to the topic ‘Usage of modal verbs in German grammar’ and could be interesting as well:

• The subject in German grammar
• The passive voice in German grammar
• The imperative in German grammar
• Exercise 1: modal verbs (müssen, sollen, …)