There is such a thing as a kit where a building for working with metal is assembled and erected in your backyard or wherever. They are like regular garden sheds but have the table space and electrical outlets that are appropriate for equipment that grinds down and joins metal. A structure like this is unlikely to catch fire, can bear the weight of a modest stack of metal, and can house wiring for welding equipment. Metal shop buildings are available online for someone who needs a specialized garage.
It is better get one of these for your workshop than a standard barn. It is because torch welding and electric welding are both dangerous arts and preferably are done in a safe environment. Having your equipment neatly attached to the wall is one way to stay safe, while building materials that reduce fire hazards are indeed highly called for.