Figurative language can include simile, metaphor, personification, hyperbole, allusion, alliteration, irony, and symbolism.
Normal fictional prose would be full of similes and metaphors in particular. Monster by Walter Dean Myers, however, is written as a film script. He probably does use similes and personifications, particularly in Steve's diary entries, but they are few and far between.
In a visual medium such as film, the most obvious figurative language to use is imagery—using the words to paint a picture in the reader's mind. Almost every scene will begin with a descriptive passage. For example, "the camera goes slowly down a grim, gray corridor." Imagery in film is not only used for exposition. It can also be used to convey emotion. For example "We see the whites of his eyes, then we see him close his eyes as the sounds of the beating stop."
From the beginning, Steve suggests that he's writing the film script as a metaphor of how unreal and strange his life has become.
Sometimes I feel like I have walked into the middle of a movie. It is a strange movie with no plot and no beginnings.
He writes it as a film script because he associates film with famous people and outlandish story lines that could never happen to him in real life. It allows him to disassociate himself from events and even the crime that he may or may not have committed.
In that regard, Steve often uses irony to paint himself in a better light. For example, he writes dialogue showing the judge and the lawyers talking casually in court about what they did for the fourth of July as if they don't have care in the world. Moments later, they are adopting serious tones and caring attitudes towards their clients as they deliver their opening statements.