Halliday & Matthiessen (1999: 241):
The metaphoric shift does not mean that the natural relationship between meaning and wording is destroyed; rather, this relationship is extended further when new domains of realisation are opened up to semantic categories through metaphor. The shift does however create a greater distance from the everyday experience; the metaphorical mode of construal makes it possible to recast that everyday experience, retaining only certain features from the congruent wording but adding others that it did not include.