The notion of Melinda finding her voice becomes the central and driving force in "Speak." David has found his voice and is comfortable in his own skin. He is completely secure with who he is and his placement in the world. Melinda needs a friend like David because of his valuing of her and because she might be able to evolve to a point where she could become like him. In the end, both students are evolving to a different point. It is that Melinda is newer to the path than David, farther along the path of dialectical understanding of self and relation to the world. It is this differentiation point that would make David an ideal friend for Melinda, who is in dire need of people or source that are defining themselves against the social order in the reclamation of their voice.
David Petrakis is different, but he knows who he is and is comfortable in himself. Melinda says that David
"...belongs to the Cybergenius clan. He has the potential to be cute when the braces come off. He is so brilliant he makes the teachers nervous. You'd think a kid like that would get beat up a lot, but the bad guys leave him alone. I have to find out his secret."
David's secret, of course, is that he is self-confident. He is not afraid to speak out, and does not allow himself to be victimized. David is not influenced by the games his high school peers play. He is straightforward and honest, his own person completely.
Melinda in contrast is unsure of her identity. She has been victimized in more ways than one, and she does not know how to deal with her feelings and the attitudes of others towards her. Melinda responds to trauma with silence, closing in on herself. Unlike David, she is unable to declare her wants and stick up for herself, and so people find it easy to mistreat her.
Melissa recognizes immediately that David is the sort of friend she needs; she says that she needs to "find out his secret," about how he gains the respect of others even while being different. David treats Melinda kindly, and says what he means. He is honest with Melinda, and expects honesty back from her; when she is hesitant about accepting his invitation to have pizza after the basketball game, he "doesn't bother to analyze (her) reluctance," accepting it at face value instead. David tells Melinda straight out that she can't "expect to make a difference unless (she) speak(s) up for (her)self." His positive attitude and genuine support gives her the courage to do just that.