Metaphors are one of the most used literary devices in the English language second only to similes. The problem with using similes is that they often cause your writing to become a mine field of quantifiers. (i.e. His breath was like the foul smell of a garbage heap and his face was like a pock marked pizza.) Metaphors can describe a scene, a character, an action or an idea in a way that the reader may not notice consciously but helps you show them what you are seeing in your mind.
Some examples of a sentence that needs work:
David's mother was an old woman, her clothes shabby and unkempt, but her eyes sparkled like new diamonds.
The grammar of this sentence is fine, but it needs something to show us what David's mother looks like and a little bit about who she is. A revision would be:
David's mother, at a glance an unassuming grimy vagrant, had within her eyes the shining light of the Holy of Holies.
This method can also be used when writing essays and trying to illustrate a difficult concept. Many of my AP students have learned this technique and it has been the difference on the exam between a score of a "4" and a "5". Students unaware of this device might write a sentence like this:
Faulkner's diction is beautiful. In this passage he illustrates how he feels about the unfair treatment of women.
A revision might look something like this:
Faulkner's diction is a looking glass through which we may view his outrage about the unfair treatment of women.
1. Pictures - Metaphors are pictures of one thing that illustrate the idea or difficult concept that you are trying to express. Think of a character or a place in your novel and what kind of mood you want to set or what kind of tone you want to convey. Brainstorm some images that are similar to these moods or tones and then work those images into the metaphorical description.
2. Talk to Others - Some of my best metaphors come from talking to people about my characters or places. If my descriptions seem flat, I hit up other writers. I tell them all about the character or place and then ask the them to tell me what these people and places make them think about. I then use these images and hammer them into metaphoric description. Above all, get into a writing group that is not online. You need face to face discussion about your writing. I think of it kind of like intervention sometimes, but it works well.
3. Classical Literature - Some of the best metaphors can also be allusions to great literature. For example, think of all the Shakespeare you have read in school and draw on his characters.
Douglas, a sad Romeo on the brink of a wedding day suicide, sat on a cracked throne in the middle of a ruined kingdom.
Remember (as I always say) writing is hard work. If you want to rise above the raucous crow-chant of mediocre writing, you must spend time at the hammer and anvil of revision. Spin your words out of fine silken thread and then weave them into a tapestry that everyone can enjoy.