A metaphor is a comparison of two unlike things, and a simile is a specific type of literary comparison that uses "like" or "as." Hughes uses both of these tools to paint the picture of his struggles. He creates a metaphor when he says, "I am black." He is talking about the color of his skin obviously, but the deeper metaphor and comparison explains that he is darkness itself; the darkness of depression has touched him because of the struggles he faces in the world. Additionally, Hughes uses a simile when he says "I have almost forgotten my dream. / But it was there then, / In front of me, / Bright like a sun -- My dream." He is saying that his dream is so bright it is like the sun. This comparison shows how important his dream is.
Hyperbole is exaggeration to make a point, and poets use it to draw attention to an emotion or a situation. Hughes writes, "To break this shadow / Into a thousand lights of sun, / Into a thousand whirling dreams / Of sun!" He wants to tear down the wall of hatred and prejudice and break it into a thousand pieces of light and a thousand beautiful dreams. This exaggeration shows how dark the wall of prejudice has become, and how anxious he is to break it apart.
Personification occurs when a poet gives human qualities or emotions to inanimate objects. Personification creates empathy and understanding in the reader. Hughes writes the wall "Rose until it touched the sky." By personifying the wall, Hughes helps the reader see it as an active, vibrant threat to the speaker's well-being. As the wall takes on life, the speaker further grasps the serious nature of the oppression with which the speaker grapples.
A symbol is an object that represents something beyond itself; the use of symbols in this poem is extensive. Hughes creates the symbol of the wall, which lasts throughout the poem. At the beginning of the poem, the wall rises up and creates shadows between the speaker and his dream. It gets thicker as the poem continues. The wall stands for the oppression the speaker faces because of his race. Toward the end, he says "Help me to shatter this darkness, / To smash this night, / To break this shadow." Instead of succumbing to the harsh wall, he decides to fight to tear it down. Hughes is explaining symbolically that he will fight to tear down the wall of racism.