Autumn, for this speaker, is not just a pretty season. A simple walk or drive turns into something closer to a vision, and the word "apocalypse" hints at endings on a huge scale. The trees are the center of it all. They "burn slowly," which is a neat way of describing red and orange leaves as if the whole landscape were quietly on fire. And they sing, telling the speaker, "This is your fate, too."
That line could sound grim, but the poem moves somewhere calmer. The song is so glorious that it changes how death looks. Life, death and rebirth blur into a single cycle, and the speaker comes away with "nothing to be feared." The mood is awe mixed with peace. The short lines and plain wording slow the poem down, almost like a quiet breath, so the final reassurance feels earned rather than forced. Autumn becomes a lesson in accepting change, delivered by the trees themselves.