Carol Ann Duffy includes the poem "Medusa" in her poetry collection entitled The World's Wife (1999). This lauded group of poems explores the stories that have not been told about historical and/or fictional women, sometimes, such as in this poem, through the voice of the female figure herself. Essentially, stories, myths, and historical narratives about men are told from women's perspectives. Women's experiences, feelings, and thoughts become the new focus. Other poems in the collection include one entitled "Mrs. Rip van Winkle," which turns the story of Rip van Winkle inside out, and one called "Frau Freud," which is essentially a complaint Mrs. Freud, the wife of famous "father of psychoanalysis" Sigmund Freud, makes while talking to other women about how sick she is of hearing about men's sexual organs. (Sex and sexuality are central to Freud's theories about the workings of the self.)
Understood in this context, the title of the poem itself—"Medusa"—tells us a lot about what we might expect from the text. According to Greek mythology, Medusa was a monstrous figure who had venomous snakes in the place of hair. Anyone who looked upon her face would turn to stone. Eventually, a hero named Perseus severs Medusa's head and takes it with him, as it still retains its ability to turn people into stone despite Medusa's death. Later, her head is given to the goddess Athena who puts it on her shield for use in battle. Medusa has come to represent or embody female rage or fury, according to some feminist interpretations.
With this background in mind, we might consider how the structure of the poem adds to or challenges our (mis)conceptions of the mythological Medusa. First, the poem itself is in first person and is, importantly, told from Medusa's own perspective. She is describing her feelings of jealousy toward the man she loves, which has resulted in her appearing monstrous, dangerous, and infuriated. The jealousy is given its own agency here; it acts of its own accord as it "turned the hairs on my head to filthy snakes," seemingly overtaking Medusa and controlling her.
Another way to parse out the themes of the poem is to pay attention to the verbs that are used. Here is a list of the most interesting ones:
These are all very physical verbs in that they evoke a sense of bodily involvement, sometimes in the form of emitting a sound or fluid (e.g., hiss, spit, spew), and sometimes resulting from the body or body part "breaking" in some way (e.g., sour, stink, spatter, shatter). The effects of this inner feeling of jealousy are very negative and very physical.
Finally, throughout the poem, we read as Medusa describes her feelings and their physical manifestations to her beloved. It is only in the last stanza that we get a sense for why she is jealous and hurt. Here, her beloved returns "with a shield for a heart / and a sword for a tongue / and your girls, your girls." We are given reason to believe that her feelings of jealousy are the result of the way this man treats her. This is the feminist twist to this interpretation of the Medusa story that is only made possible by telling the story from Medusa's perspective. The mythological version of the story does not explain why Medusa is the way she is, but here we are given a reason: She is in love with a man whose heart is presumably guarded, who does harm with the words that he says ("a sword for a tongue"), and who is promiscuous and noncommittal.