Metaphor is a trope - an figure of discourse 2. Metaphor is a function of naming by deviation 3. Metaphor appeals to a resemblance 4. This resemblance works by substituting a figurative sense for a literal sense. The substitution is not a semantical innovation - no new meaning 6.
Metaphor gives no new information about reality.
In short, the use of metaphor forces us to give a new meaning to the words used. Metaphors, in this view, are intentional errors - calculated to create new meanings. Living metaphors serve this function - dead metaphors have been so used so much that we take them as literally true. Metaphors will not be literally true - in fact if taken literally they are absurd. Poetic language does not literally say what things are, but what they are like.