Okay. Metaphors signify Structured Experience. Why?
Lakoff and Johnson, p. 156:
> Metaphors have Entailments through which they highlight and **make coherent** certain aspects of our experience. [My emphasis]
> A given metaphor may be the only way to highlight and **coherently organize** exactly those aspects of our experience. [My emphasis]
Without going overboard by using analogies to Chunking, it does seem we have a need to make experience "fit together". Possibly the Distributed Logjam metaphor fits in here: our brains can't operate unless it develops networks rich with associations. In this interpretation "coherent" is just a synonym for a strongly connected subgraph 
(using that, again, more metaphorically than literally).
> Metaphors may create realities for us, especial social realities. A metaphor may thus be a guide for future action. Such actions will, of course, fit the metaphor. This will, in turn, reinforce the power of the metaphor to make experience coherent. In this sense metaphors can be self-fulfilling prophecies.
Note that, by analogy to the Quick Example of Learning a Smell, such a use of a metaphor will strengthen it, make it more salient, make it more *valid* for you.