Writer Unboxed, answered a reader's question about generating metaphors.
I was so delighted with her "lightbulb moment" that I've reproduced the two key paragraphs here:
"I had a HUGE lightbulb moment about metaphors a few years ago, thanks to Sands Hall, whose workshop I took at the Iowa Summer Writing Festival (that same program I mentioned above.) Before that I just considered a metaphor a metaphor: they were either lovely and apt or dead and clumsy. But when Sands described how she made each character’s point of view distinct in her book Catching Heaven, she mentioned how important it was that each character’s metaphors were true to that character. And that was the lightbulb. A rancher will use different metaphors than a schoolteacher. Even if the book is in third person and not first, if the point of view is close-in to the character, you want to apply that character’s “filter” to everything – including the metaphors.One should probably resist the temptation to rely too heavily on idiosyncratic, character-based metaphors, particularly in a fantasy where the reader doesn't know the character's referential context. (Does, "He was as happy as a skurlump on a fringbol," say anything to you?)
"I took this to an extreme in my book The Kitchen Daughter, where the narrator Ginny is so obsessed with food and cooking — and so uncomfortable dealing with the wider world — that she filters absolutely everything through the lens of food. She bumps into a shoulder and it feels “like the shank end of a ham”; the voices of the people in her family she compares to orange juice, tomato juice, spearmint, espresso. In most cases your characters will draw from a larger pool, but still, the idea that there is a pool, and that it comes from that character’s particular bias and experience, that’s clutch."
That said, not only are a few well-chosen character-based metaphors a great way to contribute to the voice of the narrative, this is also a good way to avoid anachronistic metaphors if you're writing about another time or place.
Deren blogs daily at The Laws of Making.