Tom Buchanan is a rich, spoiled bully. His family is from Chicago, but has the connections in social circles to enable him to marry a trophy wife in the person of the beautiful Southern debutante, Daisy Fay, in an extravagant ceremony that featured "more pomp and circumstance than Louisville ever knew before.
At the time of the story, Tom and Daisy live in East Egg, the area of old money. Their home was "a cheerful red-and-white Georgian Colonial mansion, overlooking the bay." Tom describes it as "a nice place" but makes sure Nick knows "It belonged to Demaine, the oil man." He's prejudiced against everyone who's not like him - rich, white, and self-centered.
Tom is accustomed to getting what he wants and doesn't tolerate being crossed. He likes having Daisy for show at social gatherings, and he loves having Myrtle Wilson for actual emotional connection. He does not appreciate having the disconnect between these two alliances pointed out, as Myrtle discovered.
Some time toward midnight Tom Buchanan and Mrs. Wilson stood face to face, discussing in impassioned voices whether Mrs. Wilson had any right to mention Daisy's name. "Daisy! Daisy! Daisy!" shouted Mrs. Wilson. "I'll say it whenever I want to! Daisy! Dai-" Making a short deft movement, Tom Buchanan broke her nose with his open hand.
At the end of the book, Tom refuses to acknowledge his role in any of the events that took place between George Wilson and Gatsby. Tom and Daisy continued to support each other in their efforts to enjoy the good life, however superficial their relationship might have been.