I don't think a lot of people realize how wonderfully helpful - and powerful - metaphors are. Yes, I'm sure we're all aware that they are artful, but they are more pervasive than we generally imagine, and I find them incredibly useful for two things: conciseness, and worldbuilding.
Conciseness may not be the first thing that leaps to mind when you consider metaphors, but believe me, it works. The example that leaps to mind from my own work comes from "At Cross Purposes." I'd gone to a lot of trouble to design the bridge of my otter-aliens' ship, and I found myself describing the quality of the light, the fact that there was soft music, the room full of fish (snack bar), the pairs of otters moving and jumping, the whirling bits of light, the this, the that... It got longer and longer and I was despairing a little, because the story was already pretty long. Then I walked away from it for a while, and after a few minutes it suddenly hit me that every detail but one fit into a single metaphor:
"It's an otter nightclub!"
Once I put this thought into Lynn's mind, the whole place resolved itself into an image instantaneously. I had to do a lot less describing of pieces, and I could provide just a few details to ground my use of the metaphor, plus add the one detail (the volume of the music) which constituted the exception. I didn't have to use nearly as many words (I think I cut out at least fifty!).
One intriguing side benefit of using a single metaphor, with supporting details, instead of just a lot of piece by piece description, is the way that you can often achieve a huge leap in clarity. The metaphor becomes the unifying element for details that follow, much in the way that a topic sentence provides the thesis for a paragraph (another reason why it's important not just to throw metaphors at a story, but to have the metaphor and its supporting details match one another). With only details you can end up with a sort of intense close-up effect where the reader never gets the sense of seeing the whole object/person/place, but of seeing only the parts and struggling to put them together. In the case of describing characters, this can mean an unfortunate Frankenstinian effect!
The other thing I wanted to mention is the power of metaphors in worldbuilding. I have mentioned this before on the blog, but I was actually able to mention it at WorldCon in a panel about worldbuilding featuring Greg Bear, among others. The panel was discussing how description of the point of view character's sensory perceptions could be an important tool for worldbuilding, and I commented how important I felt judgment was as a worldbuilding tool.
The judgment of a point of view character is actually quite complex. The most basic part of this is his/her sense that something has value or not. But when we judge things, we seldom talk just about whether is something is good or bad. We talk about what it is good for. We compare it to other things in our experience. And we talk about it in terms of familiar imagery.
This is precisely where the worldbuilding comes in. Whenever we talk about what something is good for, we speak of it in terms of the activities it may be useful for - activities which are a part of our daily social lives, and which can differ greatly depending on the society in which they occur. Whenever we compare it to things in our experience, we are also revealing the nature of our past experiences in our physical and social world. And whenever we use familiar imagery, we reveal which images are the most familiar and resonant in our world.
Is my love like a red red rose, as Robert Burns once sang? Well, we can certainly guess that his world had roses in it. Does your character dream of the day when his ship will come in? That'll be a world with oceans and a nautical history. Does he feel that another character will help him land the quarry he's never taken down in a lifetime of hunting alone? Then it's highly likely his species defines itself and its life goals in terms of hunting on land (that was Rulii, so he does).
Notice that in the paragraph above, there are no alien words. Only the word "rose" is specific to a flower species in our own world. Metaphors are an excellent tool for providing worldbuilding that does not depend on the use of alien language - and since alien language is unfamiliar to (and alienates) readers, I tend to rely heavily on this type of metaphor when I'm creating alien worlds that I want readers to feel at home in.
This technique may not be a magic bullet (metaphor!) but it's certainly worth thinking about.