Avengers: Infinity War and Tony Stark:
Tony Stark had paid the ultimate price by dying so that others in the MCU could survive.
He harnessed all the six Infinity Stones and snapped Thanos along with his entire armada off their existence. Was he then just a mere human being, mortal just like us?
Guess not, simply because mortals are not able to hold Infinity Stones such as the Reality Stone or Power Stone. Yet, Tony Stark was able to hold all six of them all at the same time.
New Viral Fan Theory:
According to a viral theory, Stark could hold the six Infinity Stones because his father, Howard Stark, had given him the Super Soldier Serum that he had helped in the creation of.
The theory suggests that Stark could wield all the Infinity Stones due to his hi-tech armor along with the Serum, with many pieces of evidence that support the fan’s theory.
As the fan points out, at the beginning of Iron Man, Stark was able to survive the dangerous attack by the shrapnel that would have otherwise killed every single person.
But Stark did not just survive the attack which embedded many pieces of metal near his heart, he also did not get any other issues or infections that could have potentially followed after the attack.
Moreover, there are scenes where he is seen going to space in The Avengers or having a full moon being thrown at him in the Infinity War, along with so many other similar instances.
All this, along with being tossed around like a rag doll by the Hulk in Avengers: Age of Ultron or being beaten to a pulp by two soldiers in Captain America: Civil War.
The Super Soldier Serum:
It has been well-established that after the Super Soldier Serum was created by Dr. Erksine in Captain America: The First Avenger, Howard Stark was able to easily replicate the Serum’s formula.
This was also the reason why the Starks were assassinated by The Winter Soldier in the first place. It could then, also mean that Howard could have potentially used the Serum as an experiment on his son, at some point in one of the films.