What are some examples of figurative language used in "The Artilleryman Vision"?

This poem by Walt Whitman describes the experiences of a former artilleryman who, while he sleeps, remembers the horror of battle. There are many examples of figurative language in the poem. To identify figurative language, it's important to know what you're looking for. Essentially, figurative language covers the words, comparisons, and analogies a writer might use to help the reader picture more vividly what is being described. This includes similes and metaphors but also other types of descriptive language.
In this poem, Whitman uses the phrase: "The grape like the hum and whirr of wind." This is figurative language on a number of levels. First, we have a simile: the sound of the grape is compared to the sound of wind. Whitman also creates an evocative sensory image through the use of onomatopoeia to imitate the sound he is describing, and alliteration emphasizes this. This alliteration exists throughout the poem to a similar effect (e.g., "dreams a devilish," "suffocating smoke," etc.). Whitman is creating an aural image for us through his choice of language.
Note also the other instances of onomatopoeia in the poem that contribute to this sensory image, such as "t-h-t!" and "snap! snap!" Whitman wants us to hear the confusion of the battle; he describes sounds rather than sights to underline the fact that the artilleryman was, in his soldiering days, often blinded to what was really going on and forced to navigate only through the use of his ears.