I think on YT thunderf00t was attempting to use a mix of Sodium and potassium metals for combustion producing water and some “white clouds”.

Instead of Iron or rust, you could separate Sodium out of Salt-water and start depositing and collecting sodium metal to store under oil or some non-reactive container. Then you could use that sodium metal for later reactions.

From fission I believe the lowest stable element you get after fission ends up being mostly Iron. I suspect Fusion is also very similar after He-H-He fusion reactions I think the most stable element you can reach is also Iron.

Iron is mostly not energy-dense mostly stable element that rusts Fe-II or Fe-III or Fe-V … I think those are the non-organic iron compounds with Oxygen / hydroxide ?

So it is probably a very stupid and bad idea to use Iron as the primary energy storage since it will not have the density or the capacity to use long-term.

That is also why Li-Fe-Po batteries exist… Lithium - Phosphate ? works better with the Iron as some kind of stabilizing agent maybe ?

But this does sound a lot like a scam and not really there yet.