This is a good question. First, it is important to start off with a definition of a metaphor.
A metaphor is a literary device where a word or phrase is used to describe something to which it is not literally applicable. An example of this would be the great hymn of the Protestant Reformer, Martin Luther, when he penned, "A mighty fortress is our God."
When we come to Homer, it is important to say that he does use metaphors as much as he uses similes. An example of a metaphor in the Odyssey, is when Homer writes, "Nine years we wove a web of disaster." Another example is when Homer says: "[Odysseus is] fated to escape his noose of pain".