A metaphor is a comparison between two unlike things without using like or as. There is no like or as in this poem to make the comparison between the narrator and a stairway. In the poem she says, "Life for me ain't been no crystal stair". She compares her life to a stairway. She describes the stairway as having things like tacks, splinters, and torn up boards. These are metaphors for the obstacles she had to overcome in her life.
