Hugh Jackman's Wolverine could return to the MCU, but his future in the franchise has been challenged by Captain America: Brave New World.

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.

In Captain America: Brave New World, Adamantium is discovered in the Celestial Island, and is a key part of the worldwide treaty that Harrison Ford's Thaddeus Ross is championing. In a speech at The White House he says that the metal has numerous health properties and could be the most important discovery since Vibranium.