Butterfly assesses the role love plays in relationships and how that love interacts with gender and culture. Love is a powerful force that can lead to obliviousness of one's surroundings. The protagonist Rene Gallimard is a Frenchman residing in China and falls in love with a Chinese actor, abusing Rene as a spy. In the same respect, Rene sexually and emotionally abuses Song, the actor. The irony of Hwang's play is that both parties are extremely selfish and get nothing in the end.
The perceived gender roles in the play were actually reversed. When the reader witnesses the encounters between Rene and Song, it seems as if Rene is the dominant person in the relationship. The most profound evidence of this comes from Song's introduction of a child into the relationship after Rene has been away. The child could not have been born from the father, so the child had to have come from the mother, and thus from Song. Although the reader knows the child is not Song's, Rene is quite oblivious to this. The gender roles are clearly reciprocated when the reader sees Rene as "Butterfly" at the conclusion of the play and Song in an Armani suit. However, support of the reversal comes much earlier in the play. As much as Rene didn't want to visit song, he did anyway. The reader can see this after the experiment Rene conjures to determine if Song can live without him. Song acted coy and pretended that he/she could not exist without Rene, but Rene thought of Song frequently. Additionally, the reader sees Rene's marriage broken up when he chooses Song over Helga.
Rene chooses to be ignorant to Song's gender. There are a series of clues to the reader that Song is indeed a man. Of course, there's the sexual evidence Song describes to the judge during the final act of the play, but in the beginning of their relationship, Song has a lot of power over Rene. Rene begins going to the opera and follows Song home.