He is known for roles in films such as Manhunter (1986), Gettysburg and Tombstone (both 1993), Gods and Generals (2003), Public Enemies, Avatar and The Men Who Stare at Goats (all 2009), Conan the Barbarian (2011), and Don't Breathe (2016).

He became famous for his role as the main antagonist Colonel Miles Quaritch in James Cameron's Avatar (2009), for which he won the Saturn Award for Best Supporting Actor for his performance.

[2] Lang's father donated much of his net worth (in excess of $150 million) to charity and did not leave an inheritance to his children, believing they each needed to learn to become self-sufficient.

His interest in the Civil War has prompted him to perform at symposia of The Lincoln Forum, which, in 2020, presented him with its Richard Nelson Current Award of Achievement.

[10] Shortly before Arthur Miller's death in February 2005, Lang appeared in his long-time friend's last play, titled Finishing the Picture.

He plays a lead role in James Cameron's sci-fi epic Avatar as the villainous Colonel Miles Quaritch.

[16] In 2009, he appeared in Michael Mann's film Public Enemies as FBI Agent Charles Winstead,[17] the man widely considered to have fired the shots that killed John Dillinger,[18][19] and in Grant Heslov's The Men Who Stare at Goats alongside Jeff Bridges, Kevin Spacey, Ewan McGregor, and George Clooney.

[20] Also in 2009, he narrated the audiobook Road Rage—which combines the short stories "Duel" by Richard Matheson and "Throttle" by Stephen King and Joe Hill—and guest-starred in the Law & Order: Criminal Intent season 8 finales, "Revolution" in the role of Axel Kaspers.

[24] In February 2012, he signed on to play Mary Shannon's estranged father in a three-episode arc on the final season of the USA television series In Plain Sight.

[26] He plays Increase Mather, in a recurring role, on WGN America's first original scripted series, Salem.

He played The Blind Man in Fede Álvarez's hit horror-thriller Don't Breathe (2016), which received positive reviews.

The annual award "acknowledges the outstanding contributions by a national figure to advance the understanding and uses of history in society.