In Out of the Furnace, Casey Affleck portrays a former soldier named Rodney Baze, who ends up embroiled in an illegal fighting ring. In real life, Casey Affleck is an actor who is not a former soldier embroiled in an illegal fighting ring, so, obviously, he had to undergo a lot of training in order to portray someone who is. To make the film's many (MANY) fight scenes look real, Affleck spent two months learning basic boxing movements to utilize during the film, in addition to learning some street fighting moves as well. 

Check out this featurette on the film, which breaks down how exactly Affleck prepared for the grueling role. Out of the Furnace will be released on Blu-ray tomorrow.