These things are already entering reality. Not the giant ones, but ones that look like
Hybrid Assistive Limb (or HAL)
The HAL is already commercially available in Japan. Currently, it's targeted at people with disabilities, but it allows the wearer, any wearer, to lift up to 5 times as much as they normally can. The newest model, the HAL-5, has a system that is integrated with the wearers nervous sytem, making it the world's first fully integrated cyborg system.
And this is what the US military is working on:
At the moment, Iron Man is just entertainment. A comic book series. Some movies. But it won't be long until an iron man will be coming to a town near you!