A metaphor compares two unlike things without using "like" or "as."
For more information and examples of metaphors, check these sites.
http://www.rhlschool.com/eng3n26.htm
http://grammar.about.com/od/mo/g/metaphorterm.htm
what is a metaphor?
3 answers
It is a comparison between to unalike things NOT using the words like or as.
e.x. it's raining cats and dogs!
e.x. it's raining cats and dogs!
another e.x. a spoon full of desire