Dickinson uses the metaphor of a fly buzzing uncertainly with a blue hue to symbolize the intrusion of everyday life into the grave and meaningful experience of death. The fly's presence between the light and the speaker represents the barrier between life and the afterlife. The "light" could be interpreted as a symbol for the transition into death or the afterlife, and the fly's interruption emphasizes the unpredictability and commonplace nature that can accompany profound moments. This is my favorite line in the poem, you have to read into it to find the true beautiful meaning.

By comparing the stillness in a room with the calmness in the air during a storm, she highlights the fear and anticipation of individuals nearing death and their emotional depth. The calm before the storm symbolizes a significant event on the horizon, much like the transition into death, producing a profound emotional response from the reader.