It could also be a more emotional take. Bucky might be feeling down about his past or his current situation, and Steve is trying to comfort him. Steve holds Bucky tightly, and Bucky comments that Steve's hold makes him feel heavy in a metaphorical sense, like he's burdened by his problems. The story could then explore their relationship and how they support each other through difficult times.
Well, it could be about a situation where Steve is carrying Bucky, perhaps in a rescue mission. Steve might be struggling because Bucky is, as the title says, heavy. Maybe Bucky is injured and Steve has to carry him to safety, and the story could focus on Steve's determination and their friendship during this tough situation.
One possible plot could be a humorous situation where Steve is carrying Bucky in a rescue mission or just during a training exercise and he keeps complaining that Bucky is too heavy. Maybe it leads to some comical banter between them, like Bucky making jokes about Steve's weakling days in the past.
Maybe the physical heaviness is a way to show the physical and emotional strain in their relationship. For instance, if Steve has to constantly rescue Bucky or carry him, it could lead to some resentment or at least some challenges in their bond. But at the same time, it could also be a sign of how much Steve is willing to endure for Bucky, showing the depth of their friendship.
One plot could be set in a post - apocalyptic world where Bucky and Steve are the last hope for humanity. They have to carry the heavy burden of rebuilding society. Their relationship is strained at first but grows stronger as they work towards their common goal.
On a more serious note, if the weight is a problem during a dangerous situation like an escape, it could cause some tension at first. But as they work through it, they learn more about each other's limits and how to support one another better, which ultimately enhances their relationship.
In some fanfics, it might be justified in a complex alternate universe scenario. Maybe Bucky is mind - controlled in a way that's extremely difficult to break, and he's forced to act against Steve. However, this goes against the deep - seated friendship between them in the main canon.
One possible plot twist could be that Bucky and Steve initially protect Tony out of duty, but then they discover a deeper connection between them all. Maybe they find out that Tony has been unknowingly targeted by a common enemy from their past. Another plot twist could be that while protecting Tony, they accidentally expose a secret of Tony's that he was trying to keep hidden, which then leads to a whole new set of challenges for all of them. It could also be that the way they protect Tony causes a rift in the superhero community, as some might think they are being too overprotective or that Tony doesn't deserve such protection.
It could be about an adventure they have on the plane. Maybe they are on a mission and face some challenges together, like dealing with bad guys or handling a malfunction on the plane.
On the other hand, Steve might be more understanding than expected. He knows about Bucky's past traumas and could suspect that something else is at play. So, instead of immediately resisting, he might play along for a while, waiting for the right moment to figure out what's really going on and how to help Bucky.
One great fanfic could be 'Bucky and Steve: A Bond Beyond Time'. It delves deep into their relationship, showing how their bond is strong and unbreakable. The story might have them facing challenges together and relying on each other's strength.
Maybe in the fanfic, Bucky has been through some sort of experiment that affected his metabolism and made him weigh less. Steve, being the protective friend, starts to train with Bucky to build up his strength again. They go through a series of challenges together, both physical and emotional, as they try to get Bucky back to his normal self.