The film begins with a real, unsimulated act of fellatio between Marcos and Ana inside a seedy Mexico City hotel. Unlike pornographic framing, Reygadas shoots the scene in a cold, objective wide shot. The act is shown as banal, sad, and transactional. When the film premiered at the 2005 Cannes Film Festival, it caused walkouts and a firestorm of controversy.

Despite its philosophical ambitions, Battle in Heaven is most notorious for two specific sequences:

: The title and various scenes reference spiritual conflict, framing the protagonist's internal guilt over a botched kidnapping as a "battle" for his soul.

: The relationship between Marcos and Ana, the general’s daughter, serves as the film’s central axis of social commentary. Their sexual encounters are devoid of traditional cinematic romance, instead highlighting a raw, uncomfortable intersection of power, pity, and mutual isolation.