Halliday & Matthiessen (1999: 244-5):
The elemental metaphors are mappings from a congruent categorial domain to a metaphorical one. The primary types are set out and exemplified in Table 6(2) below. For example, the categorial domain of 'process' can be reconstrued metaphorically in terms of the domains of (i) thing and (ii) quality. (We have added "Ø" under "congruent domains": this signals that a metaphorical process may be added, to which there is no corresponding congruent form, as part of a syndrome in which the original congruent process has been metaphorised as a thing.)
Table 6(2) shows that there are clear patterns in the metaphoric shift. For example, the 'relator' can be reconstrued metaphorically in terms of any of the other types of element; but it cannot itself be a target domain in metaphors. Such particular patterns are part of more general metaphoric motifs.
