There are many figures of speech in this poem. Even the central phrase, a "narrow fellow," can be described in various terms. First, this is an example of circumlocution—Dickinson does not say outright that she is talking about a snake, but rather, uses more words than necessary to hint euphemistically at this fact. Next, it is an example of personification—the snake is not literally a "fellow," nor does he "ride" as a man might ride a horse; Dickinson is ascribing human characteristics to an animal. This personification continues in Dickinson's use of "he" and "him" pronouns to refer to the snake, and in the idea of having "met" him. This is a verb we usually only use about other humans.

There is also a simile in the second stanza: the grass "divides as with a comb." This creates a very evocative mental image of the grass being neatly parted by the snake's passage through it, like a comb parting hair.

A further metaphor, "Nature's people," is used to describe other animals—this, too, is a form of personification. Remember that personification is a type of metaphor, although of course many examples of metaphor are not also examples of personification.

Dickinson relies mainly on metaphors as she refers to the snake as a "narrow fellow ...[that] rides [the grass]," a "spotted shaft," and "a whiplash unbraiding in the sun" as it sheds its skin. She uses a simile in "the grass divides as with a comb" to describe the action of the snake moving through the grass. "Nature's people," which refers to other animals, is an example of personification while "zero at the bone," her reaction to seeing the snake, is hyperbole because it exaggerates her fear of the creature. Notice that nowhere in the poem does she actually use the word snake.