Dramatically, this increases the abuse felt by Hamlet from his mother and deepens her fall from grace as perceived by Hamlet. He is already bothered by her remarriage and her ability to forget her dead husband. Now with the Ghost's words, Gertrude is linked to Claudius amorously if not sexually. This with the other information from the Ghost causes Hamlet to suspect his mother in the murder of King Hamlet and is the basis for "The Mousetrap" scene in the play within the play. This is differentiated from "The Murder of Gonzago", scene where Claudius is the subject. In the closet scene Hamlet in lecturing his mother uses the phrase, "call you his mouse." (3.4.183). It of course heightens the confrontation between mother and son in the closet scene.
The lines: (citing the Folio)
But Vertue, as it neuer wil be moued,
Though Lewdnesse court it in a shape of Heauen:
So Lust, though to a radiant Angell link'd,
Will sate it selfe in a Celestiallbed, & prey on Garbage.
The Arden Hamlet 3d ed. offers the following interpretation:
"While Virtue could not be seduced even if Lewdness wooed it in the guise of an Angel, Lust is capable of glutting its appetite in a heavenly bed and then turning to prey on filth."
Here, the editors define garbage as "entrails, foul remains (a stronger meaning than the modern 'rubbish'."
Lust and virtue is the very thing Hamlet challenges Ophelia with in the nunnery scene. This dichotomy is thematic. Hamlet sees his mother falling from the place of gods and angels to a place inhabited by lowly animals. Animals have no faculty for rational thought, memory, or love. They are governed by instinct to sleep and feed and lust. Hamlet sees his mother and Claudius like two rutting pigs oblivious to the decorum required of nobles. Gertrude has given in to her more unnoble and undisciplined appetites.