In "Porphyria's Lover," Browning addresses the obsession the outwardly polite and prudish Victorian society had with sensational stories of horror and depravity. The themes of sex and violence and madness in this dramatic monologue speak to this obsession.
Browning turns the conventional presentation of these issues and themes, however, by making them seem natural and beautiful. Porphyria glides (line 6) in amidst the rain and the wind and shuts out the cold and the storm (line 7). She builds a fire that warms the cottage (line 9). She bares her shoulder (line 17) and lays her hair upon his cheek (line 19). These are all images that create beauty and comfort.
At a poignant (a feeling of specialness) moment, she totally gives herself to her lover, and he, trying to preserve the moment, strangles her with her own hair, painlessly, according to the speaker.
Browning forces readers to contemplate the relationship between sex and violence and power and complex madness, as well as beauty.
How you react to the poem is, of course, up to you.
In this poem, set in the mid 1800's (probably around 1834 in England, where it was written), a man is waiting in his cottage for his loved one to come to him. She is a wealthy woman who had been at a party, and someone that did not want to admit her love for him, or the relationship that they had. He was below her in station, and she was probably afraid or embarrassed about their love. When she arrives, she comes to him and puts his head on her shoulder and tells him that she loves him. In a startling move, he takes her hair and strangles her with it, in order to keep her for himself forever, and to have her there, in that state of loving her, forever.
The ending is very dramatic and shocking; it is hard not to read the poem and be shocked by it. The narrator is clearly a bit insane; he kills her and confesses the murder in the poem. His reasoning for the murder is illogical, and his maniacal glee at having gotten away with it suggests an unstable mind. To think that a man who loved someone, and who was trusted and loved in return, would strangle her so brutally out of jealousy and a fierce desire to possess, is disturbing.
I hope those thoughts helped; good luck!