A carbon dioxide shielded welding machine (commonly known as a CO₂ welding machine or MIG welder) is a welding device used to join metals using a continuous wire electrode and carbon dioxide gas as a shielding medium. It is widely used in construction, automotive repair, and metal fabrication because it is fast, efficient, and suitable for welding steel. The machine consists of a power source, a wire feeder, a welding torch (gun), a spool of welding wire, a CO₂ gas cylinder, a regulator, and a ground clamp.

In operation, the machine feeds a continuous wire electrode through the welding torch while carbon dioxide gas flows around the welding area to protect it from air contamination. When the trigger on the torch is pressed, an electric arc forms between the wire and the metal surface. The heat from the arc melts both the wire and the base metal, creating a molten pool that fuses the materials together. The shielding gas prevents oxidation and ensures a strong, clean weld. The operator moves the torch steadily along the joint to form a continuous weld bead. After welding, the metal cools and solidifies, forming a durable bond.