Deontic modality is a modality of motivation for action, for compliance with certain laws, requirements and norms. It can be expressed in the form of an order / appeal, prescription, instruction, request, recommendation, permission, persuasion, reasoning, etc. The aim of the study is to show how the genre of the text can influence the choice of explicit and implicit means and ways of expressing this type of modality in the German language, which is realized during a specific discursive practice. Popular science, legal and literary texts became our empirical material. Particular attention was paid here to the phenomenon of isomorphism of modal verbs as markers of various situations of deontic modality. Isomorphism in this case is understood as the uniformity of the ways of expressing modal shades of an utterance in different linguistic forms. Due to this characteristic of German modal verbs, which are combined into one group, primarily based on the commonality of their etymological roots, the same verb can be a marker of different situations of deontic modality, which the article shows in the use of the verb können as an example.