We have looked at Medusa as a dramatic monologue of the mythical character, but you can also think about the transformation in a metaphorical sense.
In the poem, Medusa’s ugly emotions are described metaphorically as ugly physical features. The speaker describes herself as hideous, because her emotions make her feel that way—tainted. The destructive power of jealousy turns Medusa's hair to 'filthy snakes.’ It is as if the thoughts in her head are poisonous growths which infect her physically—giving birth to hissing, spitting snakes. She describes another transformation, that of her 'bride's breath' in stanza two that 'soured, stank'. The term 'foul-mouthed' is used to give the reader an enhanced understanding of Medusa’s internal foulness. The subject being described is the speaker’s jealousy—that is, her jealous thoughts and words. Her foul-smelling breath is a metaphor for the foulness of her thoughts. The harsh image of 'bullet tears' in her eyes reflects the fact that even in sadness she is violent and harsh. One normally sees a person crying and considers that person softened and fragile. Medusa’s sadness, however, is tainted by jealousy. She will hurt others to have her man. She is even willing to hurt this 'perfect man, Greek God” himself—by making him her unwilling prisoner. She asks him, 'Are you terrified?' She would prefer the man she loves to be stone than someone else's.
The speaker Medusa imagines her own internal ugliness as outward hideousness. It is her suspicion that her Beloved is being unfaithful that leads her to these violent thoughts. As if issuing a warning, she proceeds to list creatures that she has turned to stone. A mere glance at a bee or bird renders them respectively into 'a dull grey pebble' or 'dusty gravel'. Innocent, meek animals are turned into hard, unfeeling objects: a 'housebrick' and a 'boulder'. Metaphorically, Medusa will not let anyone stop her from being with her Perfect Man, even those who have no intention to harm.