So dreamcatchersdaughter over at tumblr threw this little headcanon my way. I think her words were: There are not enough stories out there where Tony gets to use the shield and/or Thor's hammer and from then on it developed into this headcanon. I just had to write it.
Tony knows that he has no right to be upset about this, but it doesn't change the fact that he is. Whenever someone other than Steve uses the shield, he feels a little pang in his chest, because he knows damn well that he will never be allowed to use it. Howard had made it quite clear that he would never be good enough for anything that had to do with Steve Rogers, let alone the precious shield, and Steve Rogers had made no move to prove him wrong.
Sure, he was nice, and pleasant enough, Tony even dares to sometimes think they are friends, but still. Steve has made no move to allow Tony anywhere near the shield, be it for testing or using it, and Tony can take a hint.
The team is allowed to use it; Natasha and Clint make regular use of it and even Bruce and Thor have gotten the occasional training session with it. The only one who has yet to touch it at all is Tony and he knows that isn't about to happen anytime soon. It hurts, even after all this time, but Tony has made his peace with that.
There are the occasional longing glances towards the shield, and the envy whenever a training session including the shield was going on, but it isn't anything that makes Tony stop to think even for a second about it. He is used to it and he would never be so daring to just take the shield. Not if Steve so obviously doesn't want him to.
It isn't until they run into some really nasty robots, made by some over eager kid, that this changes.
The robots are armed with EMPs and while it is clearly a self-sacrificing move, they don't even hesitate to use it when they encounter Tony. With the suit out of commission, Tony has no other choice but to get out of it, even though it leaves him vulnerable and defenseless against the robots.
Steve isn't far from him, yelling at him to get back into the suit, but it won't make a difference. It will maybe take a second longer for the robot to get to him, but Tony is not about to die in a tin can.
He is about to yell that to Steve, his comm shut down with the suit, when the shield comes flying his way, only to land maybe two feet away from him.
Tony looks up, alarmed and momentarily forgetting his own predicament, because Steve would never just throw his shield like that. Something must have happened to him and if the robots are strong enough to get to Steve, Tony has no chance whatsoever.
But Steve is fine, fighting a robot with his bare hands, while he yells something at Tony that is lost in the battle noise. Steve quickly realizes that Tony doesn't understand him and he takes a second to pointedly gesture towards the shield.
Tony thinks for a second that Steve lost it, that the robot managed to smack it out of his hands and that he wants it back, and he wants Tony to throw it back. It's a second too long, because in the meantime the robot reaches him and before Tony can grab for the shield, he is hit in the head.
His head spins and Tony sees only black for moment, but when his vision clears, he notices that he stumbled closer to the shield and while he knows that he is supposed to get it back to Steve, he also knows that he will die if he doesn't use it to defend himself and so he doesn't even think about it. It's either taking the shield and making Steve angry or dying when the robot reaches him.
Tony decides an angry Steve is better than biting the dust and so he quickly bends to take the shield. It feels light, lighter than he had imagined it to be, and it handles like a dream. Tony is enraptured but when there's a screeching noise behind him, indicating that the robot is about to hit him again, he spins around, shield safely in his hand. It's so easy to smash its head in, Tony barely needs to do anything, it feels like the shield is moving on its own.
When the robot is destroyed, Tony immediately turns back to Steve. He barely registers that the fight is over, so strong is his need to get the shield back to where it belongs.
Steve is meeting him halfway and Tony hesitates when he sees the thunderous expression on his face. He's confused for a split second before he realizes what he has done and he holds the shield out to Steve.
"I'm so so sorry. Please don't be angry. I know I'm not supposed to use it, I know you don't want me to, but I had to. It would have killed me. Please don't be angry."
"You idiot!" Steve yells at him and Tony flinches slightly. It's only then that the words seem to reach Steve and he pales a bit under his cowl.
"What do you mean, I don't want you to touch the shield?" he asks and Tony defensively raises his shoulders.
"You never let me, and it's fine," is as far as he gets before Steve is yelling again.
"You think I'm angry because of that? Tony, you nearly got killed because you wouldn't take the shield! I'm angry about that. Why the hell would you even hesitate?"
"Because it's your shield?" Tony carefully asks and Steve shakes his head.
"All of you are allowed to use it. Especially when in danger. You never indicated that you would want to use it, so I didn't make you," Steve explained and comes a bit closer. He raises his hand to brush Tony's temple and it is only when Steve's gloves come away bloody that he realizes he is bleeding.
"Go to medical, get this look after. And after that you're meeting me in the gym. Bring the shield. It's time you get some training with it. We can't have that happening again."
With that Steve turns around, walking away, no doubt to check on their other team mates. Tony is unable to move, shield still in his hands, and only when he looks down does he realized that he's shaking so hard the shield is slightly vibrating.
Maybe he is badly concussed. Then this would be a hallucination and that would make more sense than everything else.
He's still staring down at the shield when Steve's boots enter his vision again. "Tony," he carefully asks. "Are you alright?"
"You left me with the shield," he points out the obvious, because Steve has yet to take it back from him. "I'm not worthy," Tony mumbles but Steve clearly picks up on it because he closes a hand over Tony's on the shield.
"Yes you are. And I'm sorry I didn't make sure you knew that earlier. I thought you knew. I trust you with my life. Of course I would also trust you with the shield."
At that Tony finally looks up again, because Steve has always been a bad liar and if this isn't true, Tony would be able to read it on his face. But he is met with a smile and nothing but truth and it takes a second to register that Steve actually means what he said.
"You sure?" he weakly asks and Steve nods.
"Positive. Are you up for a lesson? Not that you need it when I look at that robot, but one can never know, right?"
"Right. But maybe, let's wait a day or so? I'm feeling a bit faint."
Steve agrees readily to that, obviously thinking it's because of the head wound but Tony isn't so sure about that.
When Steve leaves him again he still leaves Tony in charge of the shield and Tony doesn't know what to do with that.
After that, Steve and Tony regularly train with the shield, and Tony is quickly getting comfortable with it. But the most amazing thing about this is that Steve doesn't seem to have any problems leaving the shield with Tony. It's like he said. He has no problems trusting Tony with his life and if that means trusting Tony to get the shield, which he had very stupidly left with him before, to Steve in a dangerous situation then he wasn't even worried about it. Tony was worried enough for both of them anyway. But it never stopped Tony from feeling grateful.