Medieval armor was made from a variety of materials like various metals, cloth, and leather.
Some were made of large metal plates sewn inside a leather coat or any other cloth while some were made from rings of metal chains bound together over cloth and/or leather.
Even in the past, there is evidence that the warriors wore steel armor although rare.
In the modern days, medieval armor are also made of foam and plastic, but these are mainly used as costumes and mere cosplay weapons.