“Porphyria’s Lover” is a poem about control—and the lengths to which the speaker is willing to go to achieve it. The poem’s enjambments and end-stops often reflect that desire for control. For example, line 41-42 are both end-stopped:

No pain felt she;
I am quite sure she felt no pain.

In these lines, the end-stops are definite and strong. They suggest that the speaker is unwilling to even imagine an alternative, to allow any doubt about his account of things. In this sense, the underline how he has taken control over Porphyria and excluded her personal experience from the poem.

Yet the poem's use of end-stops also registers the way that Porphyria’s presence upsets his control. The poem begins with five end-stops in a row. Only when Porphyria enters the poem in line 6 does the poem use enjambment for the first time. It then switches back and forth between enjambment and end-stop, almost as though the speaker and Porphyria are battling for control over the poem, the speaker trying to constrain the poem’s sentences and Porphyria, with her dynamism and energy pushing them past the boundaries of the line breaks.

One can see this struggle if one takes a closer look at the relationship between the poem’s rhyme scheme and its enjambments and end-stops. Poets often try to close a group of rhymes with an end-stop: doing so helps give the poem an internal structure. And “Porphyria’s Lover” starts out that way: when the speaker reaches the end of the first group of ABABB rhymes, in line 5, he also uses an end-stop: "I listened with heart fit to break." Porphyria’s entrance into the poem upsets that pattern: the next group of rhymes ends in line 10, but line 10 is enjambed—"...and from her form / Withdrew..."

Only in line 25, when the speaker fantasizes that Porphyria might “give herself to me forever,” does the speaker manage to end a group of rhymes with an end-stop. It is as though Porphyria’s independence, her energy and dynamism, upsets the control that the speaker wishes to assert over his own poem. But once the speaker gets Porphyria where he wants her, he reestablishes this control. After line 25, there's only one moment where the end of a group of rhymes doesn’t coincide with an end-stop: in line 50, where he lays her head on his shoulder. (Line 40 is technically end-stopped, but it may feel more like an enjambment because of the way the sentence continues in the next line—the speaker seems to almost lose control in that moment). In this moment, the speaker’s own passion and excitement seem to overcome his desire for control—ironically, right at the moment he achieves that control.