Pretty much every metaphor designer is inspired by Metaphors We Live By (1980), by the Berkeley linguist George Lakoff and the philosopher Mark Johnson at the University of Oregon. It’s the classic look at how metaphors structure the way we think and talk, and once you’ve read it, you can’t help but agree that, at a conceptual level, life is a journey, and arguments are wars (you take sides, there can be only one winner, evidence is a weapon). However, for the practical metaphor designer, psycholinguistic research turns out to be much more useful than philosophical commentary, because it studies how people actually encounter and process new metaphors.
http://aeon.co/magazine/culture/how-to-design-a-metaphor/