Special features of the modal verbs

 

Modal verbs form the present perfect and the past perfect tenses with the auxiliary verb haben + infinitive, instead of the past participle (Partizip II).

 

Examples
Ich habe sofort nach Haus gehen müssen.

 

However, when modal verbs function as full verbs (i.e not connected to an infinitive), they form the present perfect and the past perfect with the past participle (Partizip II).

 

Examples
Ich habe sofort nach Haus gemusst.