Here’s why Thor looked so worried when Captain America tried to lift Mjölnir in Avengers: Age of Ultron. The second Avengers film may not be as well-received as its predecessors, but it has some of the memorable moments from MCU’s original group of heroes. Its opening party sequence was particularly charming as it showed the characters relaxing, having fun with each other after they presumed that their mission was over.
This specific scene in Age of Ultron brought to the big screen one of the most fun scenes in the MCU: the team trying to lift Thor’s hammer. Almost every hero attempted to wield the Mjölnir, but even Hulk, who can go toe-to-toe against the God of Thunder, could barely move it. That’s until Captain America tried his with it. While he didn’t fully get it off the ground, he was able to ever-so-slightly shift it, getting a concerned look from Thor. This was a great foreshadowing for the Super Soldier’s eventual use of the Mjölnir in Avengers: Endgame — but in that movie, Thor was ecstatic to see his fellow Earth’s Mightiest Hero be worthy of the hammer. So why was he even worried about the possibility just several years prior?
Ultimately, this has to do with Thor’s personal arc in the MCU. The God of Thunder has gone through so much in his heroic journey in the years since he was banished to Earth by Odin to learn humility. It has not been easy for him; even after he proved once again to be worthy of the Mjölnir, and while he looked mighty and powerful, he was still emotionally fragile, demonstrated by Thor’s grief in Avengers: Infinity War after he failed to stop Thanos. At this point in his personal arc, Thor still wasn’t confident with himself, and there’s an argument to be made that even after Endgame, this remains to be the case. Thor cockily offered anyone to be the ruler of Asgard if they successfully lift his hammer; at this moment in Age of Ultron, he still hadn’t realized that being King wasn’t what he truly wanted. He firmly believed that this was his destiny and he equated his self-worth to the idea that he would one day be like his father — which is why he was so treated by the prospect of Captain America “stealing his thunder.”
It’s worth noting, however, that Endgame‘s directors and writers have contradicting views when asked whether or not Captain America was already capable of wielding the Mjölnir in Age of Ultron. Joe and Anthony Russo claim that the Super Soldier has always been worthy, only opting to not reveal it at that time so as not to offend Thor. Meanwhile, Christopher Markus and Stephen McFeely say that Steve Rogers was genuinely unable to lift the hammer as he was still being held back by lying to Iron Man about Bucky Barnes killing his parents. Joss Whedon, who wrote and directed Age of Ultron, has yet to weigh in on the matter, and whose opinion could finally clarify this confusion. Regardless of the case, however, this doesn’t have anything to do with Thor and how he reacted to Captain America’s attempt in Age of Ultron.
The interesting thing about the God of Thunder is that there’s still so much story left for him in the MCU unlike most of his fellow original Avengers. His self-realization at the end of Endgame that he doesn’t really want to be King of Asgard sets him on a new path. Hopefully, the franchise also finally shows him to be genuinely comfortable with himself and move past having to fake it as he did in this Avengers: Age of Ultron scene.