What would be some good ideas to write an extended metaphor poem about?

Usually you want to come up with something you have emotion about and then find something that could metaphorical for that emotion. This way you have substance behind the metaphor.

I'll give an example, so you can see what I mean. Say that I loved a woman, but the feeling was not returned. I'd be looking for an item that at once brings hope and pain into one's life. Some sort of dual object. For this i might use rain... it brings new life, nourishes the soul, provides sustinance... but it can also desimate a city, feel gloomy, and dampen your mood.

Like i might desire to do extra powerful than Jack - lol :) i'm no longer probable poetically susceptible, inspite of the certainty that i like Dr. Seuss. i'm doubtful if those are the varieties of words you're searching for even with the easy certainty that.