At one point in the novel, Jay Gatsby romantically describes Daisy as "the grail," alluding to the holy grail, the unattainable goal of the chivalric knights. In his quest for Daisy, whose name suggests purity, and in his romantic delusions, Gatsby perceives Daisy as the ultimate goal in his materialistic world. However, by saying that her "voice is full of money," Gatsby suggests that she is also like a material object, namely money, that can be attained.
Interestingly, this figure of speech that Gatsby employs is ironic. For one thing, Gatsby suggests that Daisy's speech is the language of the wealthy, when in reality she speaks of petty things, even foolishness. For another thing, it is not Daisy's voice at all that attracts Gatsby; it is the status of having a woman from the wealthy class that he desires. Rather than being prized for her voice and what she says, Daisy is merely a status symbol.