Halliday & Matthiessen (1999: 234):
Thus in many instances, not unexpectedly, lexical and grammatical metaphor go together. … But they are not automatically associated, and in most instances of grammatical metaphor, if we reword in a less metaphorical direction, we can retain the same lexical items, merely changing their word class [transcategorisation] (often with morphological variation, e.g. we act effectively / the effectiveness of our actions).