employ perfect rhymes—though there are often other sound similarities at the ends of lines—until the final stanza. There, she rhymes the final word of line 2, "me," with the final word of line 4, "see," giving the poem a sense of closure that it has lacked up until now as a result of her refusal to use perfect rhymes despite her embrace of perfect meter.

Throughout this entire poem, Dickinson uses iambic rhythm. The iambic rhythm uses an unstressed syllable followed by a stressed syllable, and it is a fairly common poetry rhythm. That unstressed/stressed rhythm is then repeated throughout each and every line in the entire poem. Let's use the first line of the second stanza as an example. I'll use bold for the stressed syllables.

The Eyes / around /- had wrung / them dry -

Notice that there are four iambic units in the previous line, giving the line a total of 8 syllables. Four pieces of the iambic foot give this line the rhythm and meter known as iambic tetrameter; however, Dickinson mixes up the poem. She sticks with the same rhythm, but she changes the meter. Each stanza uses tetrameter on the first and third lines, but the poem uses trimeter on lines two and four of each stanza. For example, the 2nd line of stanza number four would look like the following:

Between / the light /- and me -

Emily Dickinson carefully constructed "I heard a Fly buzz--when I died--" to have perfect iambic meter.   The word 'meter' describes the pattern of stressed and unstressed syllables in a poem.  This particular poem is written in iambic meter, which means Dickinson wrote each line to be in a pattern of an unstressed syllable followed by a stressed syllable (like Duh-DUM).  Here is an example for you:

"I heard | a Fly | buzz – when | I died – "

Even the structure of the stanzas is carefully organized to support Dickinson's iambic meter; she divided the poem into four stanzas, and each of those stanzas have the same division of syllables per line.  The first and third lines have eight syllables each (known as 'iambic tetrameter', because 'tetra' means four--so it has four iambs).  The second and fourth lines of each stanza have six syllables each (iambic trimeter).  

Emily Dickinson's poems can be enigmatic and hard to understand. In poem 591, "I heard a fly buzz - when I died," she is describing the impossible, namely, her own death. Her spirit is speaking to the reader after her body has expired, and she is describing what it felt like to go through the process of dying. Stanza two describes the mourners, stanza three describes making her last will and testament and reintroduces the fly, and the final stanza continues to describe the fly and then her final demise. Here is one way to paraphrase the first stanza, emphasizing its literal meaning: "When I passed away from this life, I heard a fly buzz. There was no other sound in the room. It was kind of like when a thunderstorm comes through, then it gets calm, and then another thunderstorm comes through. That's how quiet the air felt felt, and that's probably why I could hear the fly so clearly." 

Here's another way to paraphrase it, reading a little more emotion into it from the rest of the poem: "I remember well the moment I passed from my previous life into this one--the day my spirit left my body. One of the weirdest things was that a fly buzzed just as my spirit left. It was a fitting sound effect, perhaps, to designate how paltry and insignificant one's physical existence is in the whole scheme of things. Yes, people had been crying up a storm when they knew I was about to pass. At that particular moment, though, no one was crying. I guess they were all cried out. But soon, when they realized I was gone, the wails would resume. But at that specific moment, it was as still as the calm that occurs between two successive thunderstorms."