Halliday & Matthiessen (1999: 290):
For most types of metaphor, it is important to take account of the fact that the metaphor represents more than one construction of goings-on; the metaphor adds a further perspective on the phenomenon being represented, without displacing the perspective that is congruent Thus, Ali gave Frazier a punch is like Ali gave Frazier a rose; but it is also unlike it precisely because of its metaphorical status: it evokes a non-metaphorical agnate Ali punched Frazier. There are also grammatical distinctions between the two; for instance, there is no systematic proportion
Ali gave Frazier a rose : Ali gave a rose to Frazier : :Ali gave Frazier a punch : Ali gave a punch to Frazier
The grammatical metaphor will typically show features of the congruent perspective as well as features of the metaphorical one.