One of the coolest sights in comic book history is when someone other than Thor is found to be worthy enough to wield Thor's hammer, Mjolnir. For decades, the list was very small, but in the last 30 years or so, it has expanded a whole lot. One of the most notable "wielders" is Captain America, Thor's longtime teammate in the Avengers.
Here is a refresher course on all of the times that Cap has been deemed "worthy" in the comics over the years.
CAP FIRST PROVES WORTHY
In Thor #390 (by Tom DeFalco, Ron Frenz and Brett Breeding), Captain America is at a strange point in his career. He was stripped of both the name "Captain America" and his famous shield when the government informed him that those two things were technically theirs to do with as they pleased. When he refused to cooperate with them, he had to step down. He initially thought about just stopping being a superhero period, but ultimately he realized that he couldn't stop being a hero. So he took on a costume based on his old look and began calling himself The Captain. Black Panther made him a replacement shield that was almost as good as his original. He also returned to the Avengers (after he had initially taken a break when he was stripped of his name).
In any event, in Thor #390, Thor goes to visit the Avengers on their new headquarters on Hydro-Base. They are then attacked by the soldiers of the villainous god of death, Set. Thor is overwhelmed by bad guys and he is separated from his hammer.
The Captain goes to get the hammer to try to get it to his friend, but then Captain is seemingly overwhelmed by bad guys, as well. Or is he?
He then quickly sends the hammer to Thor (which opened up the question of whether he was truly "wielding" it or if he was just sending it to Thor).
It was made clearer at the end of the issue where Thor and Steve celebrate the day together and Thor is so touched and honored that his friend was considered worthy of the hammer.
EVEN IN THE AGE OF APOCALYPSE, CAP IS WORTHY
After the long-running second volume of What If...? ended in the late 1990s, Marvel has since treated the concept as a special event, with one-shots detailing certain "What If...?" scenarios based on famous storylines. In 2006, Rick Remender and Dave Wilkins did What If...? Age of Apocalypse, which offered a different look at the classic storyline.
This time around, instead of Apocalypse rising when Professor X was killed, Legion kills so many other people in the battle that accidentally killed his dad that the world reacted swiftly to the new threat of mutants. This delayed Apocalypse's attack on the world, so it did not come until the Marvel Age of Heroes had been established. Thus, when Apocalypse did eventually conquer the Earth, there were enough heroes to try to stop him.
Captain America was revived and he is rocking Thor's hammer...
In the end, they defeat Apocalypse by having Nathan Summers (the son of Cyclops and Jean Grey in this universe) take control of him. However, Nathan is so powered up now that he wants to go back and time and fix Legion's previous time traveling and Captain America won't have it...
DON'T WORRY ABOUT FEAR WHEN YOU HAVE CAP HERE WITH MJOLNIR
Speaking of dark stuff, a few years later, the Marvel Universe was in the grips of fear as Odin's long-lost older brother, known as "The Serpent," has decided to raze Midgard, with the help of his children (who show up in their own hammers). They possess some of the mightiest heroes and villains in the Marvel Universe. The Serpent causes widespread fear among the populace (and then feeds off of that fear to become even more powerful).
Steve Rogers had taken a break as Captain America, but his successor, Bucky Barnes, appeared to fall in battle with the Serpent, so Steve began Captain America again and he rallied the heroes of the world (plus the good citizens of the country) to fight against the Serpent, using Mjolnir as part of an epic rallying cry in Fear Itself #7 (by Matt Fraction, Stuart Immonen and Wade von Grawbadger)...
Inspirational stuff right there.