First of all, very glad to even be able to type the word "metaphor" today. On Saturday, I poured a very full glass of water directly into the keyboard of my shiny new laptop. It was mostly fine, but not all of the keys recovered. I had to spend the next 24 hours using the cut and paste function whenever I need an "m" or an "n". Needless to say, that got old pretty fast, so I walked it into the Apple store, saying, "Stop me if you've heard this one..."
But on to metaphor. I think the best metaphors are the ones that do a thousand things at once. The best way to explain this is probably by example. So here are a couple of examples of metaphors that work brilliantly:
- From Benjamin Percy's Refresh Refresh: "a no-neck linebacker with teeth like corn kernels and hands like T-bone steaks." That's a lot of information and description packed into a slim 13 words. "Corn kernels" not only tells us about the size and shape of the linebacker's teeth, but also their color. "Corn kernels" also implies something soft, like maybe his teeth are rotten. "T-bone steaks" likewise gives me a sense of size and shape, but also density and weight. It casts the linebacker's fists as being dumb or without agency, just pieces of meat. And both together tell us a fair bit about the narrator, as well as the person he's describing. Narrators should always use descriptions that are within the realm of their experiences. From this line, I glean that this narrator is a "meat and potatoes" kind of guy. I feel like I know a little bit about what he eats, and can extract from that some information about social standing, income, etc.
- From "Kavita Through Glass" by Emily Ishem Raboteau: "The pieces of colored glass were smooth and flattish and oblong, shaped like teardrops roughly the size of robin's eggs." Again, "the size of robin's eggs" does not just tell us about the size, but also shape and texture and fragility. This image combined with "teardrops" makes me think of the color blue. "Teardrops" implies that they are translucent and glassy. It also impacts the mood of the piece, bringing in a sense of sadness.
I could go and on, but I think you get the idea. Good metaphors do a lot of work for the little space they take up on the page. The other side of this, of course, is that the least successful metaphors are the ones that do nothing. I will occasionally come upon a draft that has a line like, "It sounded like a thousand Cheerios being flung forcefully against a trampoline." I don't know about you, but I have absolutely no idea what that sounds like. Rather than doing the one thing that metaphor sets out to do (give me a sound image), it instead obfuscates the tenor even more. I now need another metaphor to explain the metaphor meant to explain the original sound!
So take your cues from the authors above. Never limit yourself to illuminating just one aspect of the thing you're describing. Instead, make your metaphors work hard and save yourself some precious real estate.