Why does Tom attend Gatsby's party in The Great Gatsby? How does this scene reveal the contrast between Gatsby and Tom?
Tom attends the party in many ways to try and ruin Gatsby. Once there he is critical of everything about it, the decorations, the people that are there, the way that Gatsby behaves, anything he can be critical of, he does so. He also attempts to substantiate a rumor that Gatsby is a bootlegger and decides after the party that he will really dig into Gatsby's past and try to discredit him.
This event begins to unravel Gatsby's ascent into high society and starts the downward path to his destruction. It begins to become clear that Daisy's love for Gatsby is as false as her love for Tom and that the charade of high society is sadly a model for the love that Gatsby thinks he is going to find when he asks Daisy to abandon Tom and be at his side.
In chapter 6 of The Great Gatsby, Tom is starting to figure out that there might be something going on between Daisy and Gatsby. When Gatsby throws a party Tom and Daisy decide to join. This is ironic because Tom is at a party in West Egg, not his usual place. He is from East Egg and looks down upon the people who live in West Egg, but he goes to the party anyway.
Tom goes to the party to keep an eye on Daisy. He wants to see how she acts around Gatsby. He is not impressed by the party. He has negative remarks about the decorations and everything. Daisy, herself, seems to be having a bad time. Tom wants to discredit Gatsby in Daisy's eyes, so after hearing the bootlegging rumor, he tells Daisy that Gatsby made his money from bootlegging. Daisy is quick to jump to Gatsby's defense, saying that he has make his money from a chain of drugstores his family had. What is ironic about this is that Nick has found out the truth of who Gatsby really is.
Nick knows the whole background of Gatsby and Daisy. He is keeping it to himself for now, but there is some truth to what Tom is saying. Although Tom is having an affair of his own, he doesn't want Daisy to betray him. That would be the end to the facade that he has what everybody else wants, a good marriage to a wealthy woman and all the money he could ever want. The real tragedy is just beginning.