Norse mythology and Marvel Comics tell us that Mjolnir is composed of "uru metal," forged ages ago by the blacksmith Etri in the heart of a dying star. Presumably uru metal is magical in nature, and thus conveys the enchantment placed on it by Thor's father, Odin.
The Mjolnir wielded by Marvel's Thor was made from the mystical ore Uru. It has a long metal hilt made of Uru and is wrapped in a strip of leather with a thong to secure it around the bearer's hand.
The simple answer is no. Yes, Hulk absolutely smashes Thor to the ground with Mjolnir, but, he's holding both Thor and the hammer. Hulk wouldn't have been able to lift Mjolnir by himself, but since the God of Thunder had a firm grip on it as well, he was able to use it as a weapon against his teammate.
At one time, the order was Uru, (Thor's hammer), Adamantium, Vibranium, in that order. But, since Marvel could not use Adamantium in the movies (licensing reasons, deal with godawful Fox), Vibranium is essentially the MCU's Adamantium and the strongest metal on Earth.
Can Magneto lift Mjolnir with his metal powers? Yes he can,, but he won't get any powers. Still though having an indestructible hammer to manipulate is pretty handy With that being said Thor can also use Mjolnir to remove Magnetos forcefields …
Mjolnir is not particularly heavy, it weighs 42.3 lbs. The fact that almost no one except Thor can lift the hammer has nothing to do with it's physical weight. The hammer is enchanted so that only those deemed 'worthy' are able to wield it.
Stormbreaker has the additional power to summon the Bifröst, allowing Thor to teleport anywhere in the Nine Realms. Screen Rant has identified Stormbreaker as the more powerful of the two, based on this ability, as well as it being a much larger and edged weapon.
It's important to note that the rules around worthiness had been temporarily suspended to allow this to happen. As soon as the fight was over, Superman couldn't lift the hammer anymore. However, under normal circumstances, without any weird interference, Superman is worthy of Mjolnir.
In Marvel Comics, adamantium and vibranium weapons have gone toe-to-toe on several occasions, and the former usually comes out on top. However, in Marvel's live-action projects in the MCU and Fox's X-Men Universe, vibranium is clearly the stronger substance, and the more versatile.
Unlike Mjølnir, however, the weapon is not enchanted to prevent those deemed "unworthy" from holding it, making anybody with sufficient strength capable of using the weapon.
While the primary Thanos from Earth-616's universe was defeated and was never worthy to lift Mjolnir, it's possible that a future (or existing) variant of Thanos could.
While it has never been confirmed what Thanos' sword was made of, the Endgame battle hints that it was made of Uru or at least some metal that was as strong as the one from Nidavellir. Thanos was facing, at the same time, Mjolnir, Stormbreaker, Captain American's Vibranium Shield, and Stark's nanotech.
It turns out anyone able of holding his hand out can, doesn't it? Only people who are considered worthy are able to wield mjolnir. Cap was deemed worthy in endgame, that is why he was able to hold mjolnir.
In the MCU, five people have lifted Mjolnir: Odin, Hela, Thor, Captain America, and Jane Foster. The hammer apparently is semi-intelligent. It can determine if someone is worthy and it lets a worthy person lift it. Apparently the standards were different when Hela possessed the hammer.
Although Kratos never gets to wield the hammer, given his own extraordinary godly strength that slightly surpassed even that of Thor and even being able to hold Mjolnir back with his bare hands when Thor threw it at him, it's very likely that Kratos would be fully capable of using the hammer if he wanted to.
After bashing Thor with an entire stone pillar, Juggernaut managed to separate Thor from his hammer – but was unable to lift it as a selfish brute like him was unworthy of its power.
There's been confusion among fans about whether or not Loki is worthy of wielding Thor's hammer, but Marvel has finally confirmed that the God of Mischief can indeed lift Mjolnir. The Immortal Thor #4 complicated the issue of Loki's worthiness by not allowing him to solely be the one to lift Mjolnir.
Adamantium is a virtually indestructible steel alloy named after the fabled metal Adamantine of Greek mythology. The metal has its origins in the work of American metallurgist Dr. Myron MacLain during World War II when the U.S. government assigned him to military research and development.
It is not so much that Magneto cannot affect vibranium, but that the metal's vibratory nature and energy-absorption components can be harnessed in such a way that the Master of Magnetism meets his match.
