What is the theme of The Hunger Games?
The Hunger Games by Suzanne Collins is about the power of defiance. In a world where suffering is seen as entertainment (reminiscent of gladiatorial times), the poor are the victims of the wealthy. The government is corrupt beyond repair, and only through beating the system can Katniss change it. As seen in the later books, she eventually does change it, though at a great cost. Many could see the novel as a cautionary tale for the United States, as there are parallels between the country and Panem.
With classic dystopian tropes, The Hunger Games showcases overpowering technology versus naturalists (Katniss is a bow hunter), an evil government versus the needs of the people (only one of the districts reaps the benefits of the whole), and materialism versus love (Katniss cares for her family, where the Capitol cares only for power and wealth).
To represent this, Collins often uses fire and the mockingjay as symbols of defiance. The mockingjay is literally a failed attempt by the Capitol to spy on rebellious districts, just as Katniss, the "girl on fire," is a failed attempt to control the lower class. Literally, fire, the mockingjay, and Katniss become public symbols of defiance in the novel, as well as literary tools to demonstrate rebellion against the odds.