I'm working on a fantasy RPG where I plan for things to start out on the more realistic side in terms of weapons and armor, but let the higher end gear move into weapons and armors that wouldn't be practical in the hands of an ordinary human of our world.
One of the things I plan to do is allow players to use metal shields. The entire shield would be a solid metal plate in the same shapes as we would see shields in medieval times, likely a quarter inch in thickness, give or take. I intend for the stronger characters to wield them as easily as an ordinary warrior would wield a wooden shield of the same shape/size.
In terms of modification to the strength of these characters, I'm talking about things like muscles and bones being stronger, possibly denser, than humans of our world. Though there will also be magical means for them to achieve this level of strength, I'm focusing on ordinary physical strength training and possible changes to biology of the races of my setting. I just want to know how much stronger they need to be.
How strong would humanoids need to be in my setting to wield such a shield? Are real world humans theoretically strong enough to do that already if they trained enough to do so?