The theme of man vs. nature in this poem is best expressed through the snake as representing the forces of nature and the audience, the "we" in the poem, made up of the speaker and her companions who see the snake pass them by. Nature is shown to be a formidable, breathtaking force, literally breathtaking, as shown by the response of the speaker, as they "lost breath" to see the snake pass by them. The snake is presented as being both beautiful and deadly: he has "fierce intent," and the way he easily "quested" through the grass presents him as a lethal predator. However, at the same time, the description of how "the sun glazed his curves of diamond scale" likewise presents a picture of natural beauty that is stunning, just as the sight is one that invokes fear. The concluding remark about the snake paints him as "Cold, dark and splendid," and these adjectives seem to highlight both the danger and fear the snake inspires but also the majesty he commands.
The speaker and her companions, as shown by the last two lines of the poem, which expresses both their fear but also the recognition of the power and might of nature:
We took a deeper breath of day,
Looked at each other, and went on.
There is a sense in which the encounter with the snake gives the speaker and her companions a newfound appreciation of nature and how deadly it can be. The phrase "a deeper breath of day," seems to indicate that having seen the snake in all of its deadly might, they are now able to appreciate nature more truly and purely, recognising their own place in it. Man vs. nature therefore is reflected in the figure of the snake and how this creates a kind of epiphany in its audience: they carry on walking, but not the same, and with a newfound respect for the territory that they recognise they are intruding upon.