In the Marvel movies, the Stormbreaker lightning ax is Thor’s primary weapon starting with Avengers: Infinity War. In particular, so far there have been 4 characters who have held Stormbreaker in their hands in Marvel movies.
Groot had an interesting role in the creation of Stormbreaker. What he does can even be considered very important, it is helping to perfect a new weapon for Thor.
Initially Stormbreaker did not have an ax hilt. So Groot used his arm as an ax handle for Stormbreaker, and he suffered for it. Looking at the picture above, it’s clear that Groot has raised Stormbreaker.
Thor is the official Stormbreaker user in the MCU to date. He’s been using this powerful weapon since Infinity War, and still uses it in Endgame. It seems that he will use it in the upcoming Thor: Love and Thunder movie.
Up until Endgame, Stormbreaker hadn’t been bewitched as worthy as Mjolnir’s hammer. So, as long as the user is strong, he can use this lightning ax weapon. Which also means that some characters can use Stormbreaker even if they don’t deserve it.
In Endgame, there’s a moment when Thor tries to summon Stormbreaker. But Stormbreaker was caught by Thanos and he used it to harm Thor himself. Fortunately, Captain America then helped Thor.
4. Captain America
During the final battle in Endgame, there was a moment when Captain America accidentally summoned Stormbreaker instead of Mjolnir. The reason may be that Mjolnir fell into Thor’s hands first. If you look closely at the situation at that time, Mjolnir was summoned into Thor’s hands first, so Captain America was able to summon Stormbreaker later.
But soon, Thor and Captain America exchanged weapons. Thor gives Mjolnir to Cap, and Cap returns Stormbreaker to Thor. Seeing as Stormbreaker was somehow summoned into Cap’s hands, it seemed he was deemed worthy to take hold of Thor’s new weapon.