Metal drums are rolled steel cylindrical structures, with capacities ranging from 5 to 220 liters, Metal drums are classified into two groups, fixed or movable cover cap, , depending on the product to be packaged is solid, pasty, dust or liquid.

Drums of mobile cover cap are suitable for packaging of solid, dusty and pasty products and drums of fixed cover cap are suitable for packaging liquid products. Mobile cover caps, as its name implies, are removable and can be attached to the body by a ring with different types of lock (lever, spring or screw) Depending on the type of product to be transported, the inner wall of drums can be neutral (no coating, so the product is in direct contact with the metal) or coated with epoxy (or any of its derivatives). The coatings reduce or slow the atmospheric oxidation of the metal, such as attacks that can suffer the metal to be in contact with aggressive products.

To be noted that there are composed drums with have inside a plastic container usually made of high density polyethylene. Drums intended to contain hazardous materials must be duly certified.