In this poem, Dickinson presents an ironic portrait of death, relying on unexpected elements to make death seem ordinary and commonplace.

The line opens with a point of situational irony. As the speaker takes her final breath, the final earthly sound that registers in her consciousness is the buzzing of a fly. This is not what readers expect; religious readers might expect a heavenly chorus to welcome her into the afterlife, for example. Instead, her ears are filled with the sounds of a common earthly annoyance. Consider the way humans treat flies: swatting, slapping, shooing. As the speaker lies trapped in an earthly body that is no longer capable of movement, it is the common fly that enjoys its freedom.

Flies are also associated with death itself. Fly larvae are quite effective decomposers. Ironically, this fly seems to have arrived a bit early—just in time for the speaker to recognize its presence and possibly its motives.

Those who gather around the bed of the speaker in those final moments wait in anticipation of God, her "King," to claim her soul. They feel that they are "witnesse[s]" to an incredible spiritual moment at the end of the speaker's life. Ironically, the speaker doesn't see the face of God in those final moments; instead, the "light" in her room, which symbolizes faith and goodness, is blocked by a "stumbling" fly. What an anticlimactic moment!

The irony in "I heard a Fly buzz—when I died—" demonstrates the everyday and commonplace nature of death. The speaker's final moments reflect neither horror nor the miraculous; instead, the irony stresses the natural progression of the human form.