-Does it dry up like a raisin in the sun?
-Or fester like a sore-and then run?
-Does it stink like rotten meat?
-Or crust and sugar over-like a syrupy sweet?
-Maybe it just sags like a heavy load.
These are similes because they are making a comparison and are using the term "like".
-Or does it explode?
This is the only metaphor in the poem because the comparison is not expressed but is created in this line.