Spirituality is another theme that’s lurking around the edges. "I Heard a Fly Buzz When I Died" deals with death and what comes after, and the speaker herself is dead. Because of that, we pretty much need some spiritual framework to deal with what’s going on here. Dickinson doesn’t come out and say what happens after death, but with all this talk about the King, and the final Onset, and so forth, it definitely has to be on our minds.
The King is a direct reference to God. In this poem, the image of his final arrival is contrasted with the dirty, evil image of the fly, which represents the misery of human life.