Monster is a true crime movie based on the life of Aileen Wuornos, a prostitute turned serial killer who murdered several men in Florida during the late 1980s and early 1990s. The film delves into Wuornos' troubled past and explores the psychological factors that led her to commit these heinous crimes. Charlize Theron's transformative performance earned her an Academy Award for Best Actress, making Monster a compelling and haunting portrayal of a real-life criminal.