A drum (also called a barrel) is a cylindrical shipping container used for shipping bulk cargo. Drums can be made of steel, dense paperboard (commonly called a fiber drum), or plastic, and are generally used for the transportation and storage of liquids and powders. Drums are often stackable, and have dimensions designed for efficient warehouse and logistics use. This type of packaging is frequently certified for transporting dangerous goods. Proper shipment requires the drum to comply with all applicable regulations.

Steel drums are ubiquitous industrial shipping containers. They are manufactured from sheets of cold rolled steel formed into a tube and welded along the side seam. Stainless steel, nickel, and special alloys are occasionally used. The bottom head is permanently attached by the manufacturer. Two primary options are available for the top head:

Henry Wehrhahn, employee of Nellie Bly's Iron Clad Manufacturing Company of New York, received two patents in December 1905 that would lead to the modern 55-gallon steel drum Use of 200-litre drums became widespread in World War II, the first war in which trucks, cold rolled steel, stamp or pattern forging machinery and welding were widely available. They were first utilized by the Axis powers (Germany and Italy), but were quickly adopted by Allies. The drums helped win the Guadalcanal campaign in the first U.S. offensive in the South Pacific Theater. The U.S. Navy could not maintain command of the sea long enough to offload aviation gasoline for aircraft ashore, so the drums were often transported to the island on fast ships, such as destroyers, and shoved over the sides (or, time permitting, lowered in cargo nets). Because gasoline's density is much less than that of water, the drums floated. Navy Seabees in small craft corralled the drums.

A wide variety of constructions and sizes are available. When the intended use is for shipment of dangerous goods (hazardous materials), strict regulatory requirements are applicable. Coordinated by the UN, countries and regional authorities require drum construction and the demonstrated performance of severe testing. The Industrial Steel Drum Institute has also provided guidance for conducting the tests. Drums have embossed symbols to identify certification for shipment of certain types of products.

Many drums nominally measure just under 880 millimetres (35 in) tall with a diameter just under 610 millimetres (24 in), and have a common nominal volume of 208 litres (55 US gal) whereas the barrel volume of crude oil is 42 US gallons (159 L). In the United States, 25-US-gallon (95-litre) drums are also in common use and have the same height. This allows easy stacking of mixed pallets. Barrels can be constructed of plastic, laminated paperboard or steel.

Drums have top and (usually) bottom chimes or rims: sometimes called chines. Most steel drums have reinforcing rolling hoops or rings of thickened metal or plastic. This sufficiently strengthens them so that they can readily be turned on their sides and rolled when filled with heavy materials, like liquids. Over short to medium distances, drums can be tipped and rolled on the bottom rim while being held at an angle, balanced, and rotated with a two-handed top grip that also supplies the torque (rotational or rolling force).

The open-top sub-type is sealed by a mechanical ring clamp (concave inwards) that exerts sufficient pressure to hold many non-volatile liquids and make an airtight seal against a gasket, as it exerts force inward and downward when tightened by a normal three-quarter inch wrench or ratchet wrench. Tops exist with bung holes as above, and these hybrid drums with lid can be used to ship many non-volatile liquids as well as industrial powders. Many drums are used to ship and store powdered products as well as liquids, such as plastic beads for injection moulding, extrusion, and purified industrial grade powders like cleansers (e.g., fertilizers, and powdered aluminum). If used to transport dangerous goods across international boundaries, they may need to have UN certification. In general, drum usage is limited to wholesale distribution of bulk products, which are then further processed or sub-divided in a factory.

These metal drums have two openings with flanges, often 51 millimetres (2 in) NPS and 19 millimetres (0.75 in) NPS in diameter. Once the drums are filled, the plugs (bungs) are screwed in the flanges using pneumatic or hand-operated bung tightener (plug wrench). To secure the contents of the drums against theft and adulteration during shipment, cap-seals made of metal and other types like metal-plastic laminates are used. These cap-seals sit on top of the flanges and are crimped, using a drum cap-seal crimping tool, also called a drum cap sealer. Once cap-seals are crimped, the plugs can be unscrewed only by breaking these cap-seals. Pneumatic and hand-operated cap-seal crimping tools are available. Pneumatic ones are used in production lines for high production.