When you must convey your complex ideas simply, pick your metaphor's carefully. Good metaphors can make a complex and obtuse world seem exciting and accessible.
…But bad metaphors can do a great disservice to the public understanding of science. The idea of the “evolutionary ladder” perpetuates the myth that evolution is about a steady linear march towards complexity. The militaristic metaphor of the “war on cancer” threatens to undervalue achievements in treatment that fall short of a total cure. The idea of the brain as a computer creates all sorts of misconceptions about how different parts of the brain work, how memories are stored and whether we will ever be able to download or upload our minds.