Metaphor for good and evil
The most obvious metaphor that Mead alludes to throughout the novel, is the idea of good vs evil and this is physically depicted by the contrast between the Strigoi and Moroi. They both are descendants from the biblical story of Abel and Cain, with one epitomizing all that is bad with the world and the other a representation of all that is good and true.
Metaphor for humanity
The concept of a Damphir like Dimitri becoming a Strigoi is an allusion to human nature and the grey areas that subsists in individuals. Despite becoming a Strigoi, and therefore inherently evil, Dimitri shows compassion when he kidnaps Rose instead of killing her. Indeed, he even expresses his wishes to be with her and gives her time to make the choice herself of becoming Strigoi rather than forcing it upon her. This references Dimitri’s past life as a good and honest man with strict morals. Even Strigoi, these characteristics shine through. There is still some humanity left in him to spare Rose.
Metaphor for Feminism
Rose herself is a metaphor for what a woman can be – she is, at the heart of it, a warrior which is a stark contrast to the other Dhampir women in this story, such as Viktoria and Olena. Indeed, she dispels all notions of how a women is supposed to behave and conform to the patriarchy, when Abe orders her to return home and when Dimitri uses her as a blood-whore – she manages to escape the stronghold they had her in and makes her own path, eventually killing Dimitri.