I the book where Lyra is talking to Iofur Raknison, and trying to lie to him about being a daemon, Iofur speaks, and the book says "the flies left his mouth like tiny words", which is obviously meant to be "the words left his mouth like tiny flies", which is a strange metaphor anyway.
If you go back a page it clearly says, 'When he spoke, he waved a paw in front of his mouth to disloge the flies that clustered there' I think the SIMILE, not metaphore because it has 'like in it' is saying that the flies flew out when he spoke like they WERE the words he was speaking.