American Psycho is essentially a movie about a man that, as the title describes, is a psychopath. He doesn’t hold back on the rage that consumes him as he goes on a killing spree, catalyzed by the greed, lust and jealously he feels towards the people around him. However, everyone that knows him thinks him a nice, stable human because of how composed he is.
It is not only a battle within Bateman, as he does actually not like the part of him that kills - he likes it while he is doing it - but does understand that it is wrong, as is shown when he tells everyone the truth. It is also a battle in the society, to not believe everything you see and understand. There might be more under the surface than originally thought. When Bateman finally confesses his crimes, perhaps realizing that the only way he can be controlled in behind bars, no one believes him.
The movie and the book alike have been told to be metaphors for the American capitalist market today, as well. This is because the people on top, just like Bateman is on top in his workplace, are killing those below, destroying what they have spent time building, as well as destroying the countries economy and environment. The difference is that everyone is aware of this phenomena - though similarly to Bateman’s case - no one tries stopping them and they go unpunished.
