Sure. What it can stop will depend on the thickness of the iron, and the capabilities of the projectile being fired at it.
Bullets
Plastic is not an effective material for deflecting bullets as it does not provide sufficient resistance or strength to stop a bullet's force. Bullets can easily penetrate through most types of plastic materials. Specialized bulletproof materials like kevlar, aramid fiber, or composite ceramics are used to deflect or stop bullets effectively.
The backstop. Usually a sheet of metal, set at an angle, bullets striking it are deflected down. Some strike a bed of sand, some water, some are deflected into a large round metal pipe, where the bullets spin until they stop.
by buying a new iron
Depends on caliber & velocity of the bullet.
At the end of the first movie matrix
If there is no oxygen available, iron can not form iron oxide
That depends on the level that the vest is rated for. For example, a NIJ levvel IIa vest will stop some types of bullets. A NIJ level II will stop even more types of bullets. A NIJ level IIIa will stop still more types of bullets. NIJ levels are I, IIa, II, IIIa, III, IV, and Special.
A cowboy gun is normally a revolver, which has six holes for the bullets to go in. But the cowboy would only put five bullets in for safety reasons. It was to stop the gun firing whilst it is in his pocket.
Noop. Even if you had a bullet that was attracted to a magnet (like an iron bullet), it would have too much kinetic energy to be effected. I guess if you had a really big and thick magnet, it could stop a bullet, just like a book can sometimes stop a bullet. This has nothing to do with magnetism, but just the interaction of mass.
Kevlar is used to stop some bullets. Normally it will stop pistol rounds but other rounds , especially an anti tank round.
it can not stop bullets so why wear it?