Let's define the literary term, "figures of speech." Generally, what is meant is that either the writer has created an unexpected comparison ("Shall I compare thee to a summer's day?") or when a writer alters the conventional meaning of a word or concept, often by using irony and metaphors.
In Faulkner's tale, it is irony that prevails as far as use of figures of speech. When Emily begins dating Homer, the townsfolk are all abuzz, especially the older generation who cannot give Emily any leeway in her romance with a Northerner, "who said that even grief could not cause a real lady to forget noblesse oblige - without calling it noblesse oblige." (Noblesse oblige means that those who are in the upper classes are to be socially responsible to those less fortunate than themselves.) The irony here is that the townspeople do not want to extend to Emily the benefits that come with being deemed noblesse oblige but they still expect her to adhere to her social responsibilities.
Faulkner also makes use of metaphors. When she purchases poison, she "opened the package at home (and) there was written on the box, under the skull and bones, "For rats." The poison is not for a literal rat, but a metaphorical rat, Homer.
Another metaphor is "the newer generation became the backbone and spirit of the town." Obviously, they are not literally the backbone and spirit, but this is a way to express their feelings.
Faulker also uses point of view to create a sense of mystery. Since you do not know who is telling the story you do not know the real truth. Creating a sense of mystery, luring you to continue reading.