To start with the setting, Browning describes the stormy weather at nighttime, the "sullen" wind, which tears down the trees with "spite" and angers the lake. The purpose of detailing the bad weather is to compare itself to the speaker's mood, that, he is angry and sullen. But, the arrival of Porphyria at the cottage "blazes up" the place, shutting "the cold out and the storm," and changing the tone to a rather warmer and comfortable one. Yet, the Lover's solemn mood remains since he does not reply when she calls him or react when she seduces him with her sexual attraction.
The Lover also mentions that Porphyria is "too weak...to set...struggling passion free," that, she has "vainer ties" to separate, and also her love is "in vain." These prove that Porphyria is tied to a wealthy upper social class, perhaps, to another rich lover, while her Lover is of a lower status, and this explains his anger.
Then, by reconsidering that Porphyria has come all her way through the storm just to meet him, the Lover finds confidence in her love again. This is an example of his conflicting thoughts. After pondering what to do, he finally decides to strangle her to death with her own hair.
The theme of sin is evident here but the reader feels that he has not killed her because of hatred and anger, but of compassion and love. So, the sin is itself less obvious. Furthermore, he is convinced that Porphyria does not blame him due to her laughing "blue eyes" and her "smiling rosy little head." He also mentions that it is her "wish" to be killed. Finally, he states that God has not judged him, indicating that his action is forgiven.
The change in power of passivity is also obvious in a way that Porphyria has been the dominant figure at first, taking in charge of lighting up the cottage and even controlling her Lover's arms. Here, Porphyria is the active character while the Lover is a passive one. Then, suddenly, the power shifts to the speaker when he strangles her to death and props "her head up as before." The reverse event occurs.
Looking at the characters, Porphyria and her Lover are a complete contrast to one another. While the description of the first is in bright colours ("smooth white shoulder," "yellow hair," "blue eyes," "rosy little head"), that of the latter is in dull ones ("pale"). She is talkative while he is silent throughout the poem. She is active whereas he is passive, vice versa.
Regarding imagery, colours are used as adjectives to exemplify the character's mood. This visual imagery is mostly used to describe Porphyria, instead of the speaker. Though the speaker's solemn mood is supported just by the adjective, "pale," Porphyria's description is portrayed in bright, vivid colours, signifying her positive, pleasant, affectionate mood.
Talking about the poetic devices, personification is used at the beginning of the poem. Here, the storm is given human qualities when its "sullen wind" is "awake" and tears down the trees in "spite." {"Laughed the blue eyes without a stain." Porphyria's eyes are personified, indicating that they, too, have human qualities, that of cheerfulness by what her Lover has done to her. This is also a synecdoche since the eyes represent the whole body while at the same time, is a metaphor. Stainless probably means that upon death, her sin of cheating on the speaker are gone.}
This personification, again, shows the speaker's mood as well. Punctuation is also important. Caesura has been used to interrupt Porphyria's actions by introducing the Lover's thoughts.
E.g. Murmuring how she loved me — she
Too weak, for all her heart's endeavour,
To set its struggling passion free
From pride, and vainer ties dissever
Although Porphyria is expressing her love in words, her Lover interrupts her by thinking and convincing himself that her passion is too little. Even if she tries to persuade him, unless she breaks off her bonds, her efforts will be useless. Exclamation marks have been applied to show the speaker's convinced state of mind and his firm beliefs.
E.g. And I, its love, am gained instead!
And yet God has not said a word!
In the first verse, the speaker is absolutely certain that he possesses Porphyria now that he has killed her. Then, in the second, he believes that he will not receive punishment from God since he has done the right thing.
Relating to symbolism, there are altogether four symbols in the poem. First of all is Porphyria's yellow/blond hair. This is a memorable image since the Lover has used it to kill her at the end of the poem. Visual imagery can also be seen as blond exemplifies angelic purity. However, the verse, "let the damp hair fall,” can be interpreted that Porphyria is a fallen woman (who has sex outside marriage). Secondly, the storm, mentioned as above, has the mood similar to the speaker and Porphyria can shut it out with her warmth. The third symbol is the eyes."I looked up at her eyes / Happy and proud; at last I knew." It is ambiguous that whether Porphyria or her Lover is happy and proud but it is certain for him that her love is real. The speaker then compares her eyes to "a shut bud that holds a bee." This simile shows the speaker's care of opening the eye-lids, in fear that of getting stung by her eyes, and the alliteration of repeating 'b' sounds further emphasizes this. {*}
In conclusion, "Porphyria's Lover" is Browning's attempt to explain the mechanics of human psychology through the themes of love, passion, desire and sensuousness. His traditional technique of using the dramatic monologue exposes a single character, in this case, Porphyria's Lover's personality (development of his feelings and thoughts). Browning has also employed symbols and imagery to support his themes throughout the whole poem.