Welding is the most common way of permanently joining metal parts. In this process, heat is applied to metal pieces, melting and fusing them to form a permanent bond. Because of its strength, welding is used in shipbuilding, automobile manufacturing and repair, aerospace applications, and thousands of other manufacturing activities. Welding also is used to join beams in the construction of buildings, bridges, and other structures and to join pipes in pipelines, powerplants, and refineries.

Welders may work in a wide variety of industries, from car racing to manufacturing. The work done in the different industries and the equipment used may vary greatly. The most common and simplest type of welding today is arc welding, which uses electrical currents to create heat and bond metals together, but there are over 100 different processes that a welder can employ. The type of weld used is normally determined by the types of metals being joined and the conditions under which the welding is to take place. Steel, for instance, can be welded more easily than titanium. Some of these processes involve manually using a rod and heat to join metals, while others are semiautomatic, with a welding machine feeding wire to bond materials. Automated welding, done completely by robots, is increasingly being used in the manufacturing industry.

Like welders, soldering and brazing workers use molten metal to join two pieces of metal. However, the metal added during the soldering and brazing process has a melting point lower than that of the piece, so only the added metal is melted, not the piece. Soldering uses metals with a melting point below 840 degrees Fahrenheit; brazing uses metals with a higher melting point. Because soldering and brazing do not melt the pieces being joined, these processes normally do not create the distortions or weaknesses in the pieces that can occur with welding. Soldering commonly is used to make electrical and electronic circuit boards, such as computer chips. Soldering workers tend to work with small pieces that must be precisely positioned. Brazing often is used to connect copper plumbing pipes and thinner metals that the higher temperatures of welding would warp. Brazing also can be used to apply coatings to parts to reduce wear and protect against corrosion.