There, adamantium is a man-made steel alloy. In the 616 timeline, however, we've just found out its origin is as alien as vibranium's, and Earth's scientists are considering it an all-new element. Red Hulk's appearance in the fourth Captain America movie brings back the quite silly Marvel science of gamma rays to the forefront of the MCU.

That's because Captain America: Brave New World brings adamantium into the fold. The substance shows up in the body of the Celestial that emerged from the Indian Ocean in Eternals. Now, it's the cause of international conflict, as major world powers try to control the world's only known adamantium supply.

Brave New World still opened with a haul at the box office last weekend, and the film is set to pass another major milestone today. Brave New World, which features the big-screen debut of Anthony Mackie as Captain America,