The contribution addresses the notion of grammatical metaphor, developed within Systemic Functional Linguistics (SFL; Halliday 1985), focusing on the category of interpersonal metaphors, which are related to the lexico-grammatical expression of interpersonal meanings. Interpersonal metaphors in SFL are further divided into metaphors of Mood and metaphors of Modality (e.g. Halliday and Matthiessen 2004: 627 ff.). Interpersonal metaphors in general have attracted less attention than ideational metaphors, another category of grammatical metaphor, despite their potential significance for interaction-oriented disciplines. The identification of interpersonal metaphors, in particular, remains an issue. Working on a corpus of reply posts by doctors and nurses on the health forum of doctorslounge.com (CORP corpus), the author proposes two principles that can be applied to retrieve metaphors of Mood and metaphors of Modality in text, thus contributing to a consistent description of interpersonal metaphors and of the 'metaphoric syndrome'. CITED REFERENCES: Halliday, M.A.K. 1985. An Introduction to Functional Grammar, first edition. London: Arnold. Halliday, M.A.K. and Matthiessen, C.M.I.M. 2004. An Introduction to Functional Grammar, third edition. London: Arnold.