In the right hands they can be a clever way to get your point across. They can enrich a story and truly make it come alive to your audience, but at their worst metaphor and similes will shake your readers like the testicles of a fat man doing jumping jacks.
See what I mean? Jarring.
Or worse. All your metaphors and similes are cliched, in which case they are as worthless as tits on a bore hog.
Not too long ago I went to a childrens mass in which the homily was being delivered by a young priest. The priest had great intentions. He was trying to teach the kids about God's ability to uplift and comfort by comparing Him to a hot air balloon. Perhaps it worked for the kids but this jaded adult couldn't get passed the word choices he used ... hot air, windbag, nothingness. The homily sent my mind reeling away from the priest intended direction and truthfully I barely heard the last half.
The same thing can happen in a book. A writer must match the words with the genre. A historical writer, whether it be medieval western or even World War I writer would not want to describe something as being as shiny as a cubic zirconium.
Likewise it should match the scene's tone and tempo. You wouldn't want to write ... She wrapping her legs around his bare waist and clung to him tightly, like piece of chewed gum to to the underside of a diner table, while writing a sex scene, but that same simile might work if some guy was trying to escape a bad relationship with an overly clinging girlfriend.
I'm a big fan of metaphors and perhaps rely on them a bit too much especially when writing humor. Here is a scene from my story Plundered Booty, which is available in the anthology Deadly By The Dozen.
I joined the other salesmen in pretending to study the sticker of a candy apple red Mustang. That convertible pony was a hot ride, but it had sat in the middle of the showroom for a couple of weeks. What they were really sizing up was their chances with this new girl. To tell the truth, I wasn’t even sure Junior had a chance with this one.
Hair darker than a new set of Michelin’s. Lips that put the gloss on that Mustang to shame. A body with more curves than a Porsche. But it was those eyes that got me.
Bright, innocent eyes. Big and round like the headlights of a late-fifties sedan. The kind of eyes that said, I got a big block under the hood, but I’d never use my power for mere thrills. I’m only looking to get you safely to your destination.
I trusted her from the very moment she batted those long black lashes and gazed my direction. Some would say that was my first mistake. And maybe they’re right. Those same people would say I fell in love with her right then and there. But they’re wrong about that. At the time, I still loved my wife.
The first person narrator of this story, Hank Zybeck is a car salesman, and I use many car references throughout because they fit the character. Hank is a simple man with few interests -- Cars, Pirates, and Food. So anytime I needed to show the reader what Hank was thinking I drew from this pool.
Word spread among our wives faster than a puddle of oil beneath a Chevy, and all of us got stained.
Hank is a Ford man so Chevy is almost a dirty word in his vocabulary so by using it in conjunction with an oil leak the reader understands this is a bad event without me having to actually say so.
I'm not sure I have a point to this post other than to warn against the dangers of metaphors and similes and to urge my fellow writers to stop, think about the characters world. Ponder the story at hand and create imagery that conveys the message you want to send. You don't want to be the kind of writers that portrays God as a windbag full of hot air.