Start with a good definition of the word: http://www.answers.com/metamorphosis
Then list the events in the story that illustrate what this word means, and any actions or reactions because of these events.
CAUTION: If you write all of this in the chronological order of the story, it'll seem as if you are simply retelling the story. Any teacher will not accept simple summary in place of analysis. So my suggestion is that you treat this like a definition essay assignment.