For his first four movies in the MCU, Chris Hemsworth’s Thor was inseparable from his mystical hammer Mjolnir. Until it was destroyed by his evil sister Hela in Thor: Ragnarok. When preparing to battle Thanos in Avengers: Infinity War, however, the God of Thunder endeavored to get himself a new weapon, enlisting Eitri and the forges of Nidavellir to help him. The result was Stormbreaker, which seems to be more powerful than Mjolnir in every way, except one.
Over the course of Infinity War and Avengers: Endgame, Stormbreaker is proven to be even more durable and useful than his old hammer. It’s able to cut through the combined blast of all six Infinity Stones and it can even summon the Bifrost itself. But, unlike Mjolnir, it can be lifted by anyone. In IW, teenage Groot is able to hold it when sacrificing his own arm to create a handle for it and Captain America briefly wields it during the Wakandan battle.
Though it just so happens that Steve Rogers is worthy, he didn’t need to be to pick up Stormbreaker. The reason Mjolnir can only be wielded by Thor is because of the enchantment placed upon it by Odin in the first Thor movie. While Stormbreaker is undoubtedly strengthened by various spells and magical forces, Odin’s proclamation is not one of them. And this may well prove important to the future of the MCU.
In the comics, Thor’s horse-faced alien pal Beta Ray Bill is the owner of Stormbreaker and given his popularity, there’s an expectation that the Corbinite will finally appear in Thor: Love and Thunder. And if he does, the fact that anyone can use the axe should make it easy for him to be gifted Stormbreaker by the Asgardian. Likewise, he’ll probably give Jane Foster Mjolnir, too. So, Thor may end the film without either weapon, which would certainly fit in with the speculation that the hero will retire in Thor: Love and Thunder.