The first five lines of “Porphyria’s Lover” establish the poem’s mood and setting. The speaker is in an isolated, rural place. It’s rainy and windy, violently so. The wind is churning up big waves on the lake and breaking the tops of the elm trees—and it seems to be doing so on purpose, personified as acting out of “spite,” or bitter anger. Note the consonance of the /t/ sounds in line 3: “It tore the elm-tops down for spite.” The /t/ sound is harsh and percussive, and it echoes the violence of the wind: one can almost hear the trees cracking. The speaker doesn't seem to be in a good mental place, as he describes himself listening to the wind “with heart fit to break.” This all sets the tone for the poem, which will be as violent and disturbing as the storm outside.
The poem's form is also established right up top. It is written in iambic tetrameter, meaning there are four iambs (unstressed-stressed) in each line:
The rain set early in to-night,
The poem’s meter starts off strong and regular, and it stays that way. There are relatively few metrical substitutions in the poem—so when they do appear, they are striking and surprising. There’s something a little strange about the poem’s metrical perfection, and it will become clear soon enough that it reflects the speaker's obsession with control.
The poem follows a rather unusual rhyme scheme, ABABB (it is actually sometimes printed in a series of five-line stanzas to better display this rhyme scheme). Its first few lines look like a common ABAB quatrain, but then there's this extra line tacked on. Once again, it feels like there’s something a little off here, something obsessive, in the poem’s form: the speaker can’t quite let go and move onto the next rhyme. This obsessive, controlling energy is also evident, at least initially, in the poem’s use of end-stop: each of the poem’s first five lines are end-stopped. (When Porphyria enters in line 6 she disrupts this contained, controlled poetic world.)