According to Latino Review on Feb. 15, Marvel offered Jason Momoa the part of Drax the Destroyer in "Guardians of the Galaxy". Isiah Mustafa, Dave Bautista, and Brian Patrick also auditioned for the part, but Momoa did so well, they offered it to him on the spot.
Momoa also played in the movie "Conan the Barbarian" by LionsGate, "Bullet to the Head" along with Sylvester Stallone, and a big regular on the series "Stargate: Altantis". He is well known for his portrayal as Khal Drogo in the first season of "Game of Thrones".
For a sizable guy, he does well with choreographed martial arts. For "Conan" he had an intense six week work out regimen that included up to six hours of martial arts and sword play. In comparison to Arnold Schwarzenegger, Momoa prepared himself for the role by reading some of Robert E. Howard's "Conan" books which gave him an idea of the mannerisms and lifestyle of the character. He had a goal to achieve of gaining 10 pounds of muscle for the movie, and chances are he'll have to make similar preparations to live up the expectations of Drax.
It's up to fans to determine if Momoa can be seen playing one of the guardians and does to seem have a similar physique for it.