Welding is a process used to fuse metal together. It involves the use of heat and pressure to join two pieces of metal together. The most common type of welding is arc welding, which uses an electric current to create an arc between two pieces of metal, melting them together. Other types of welding include gas welding, oxy-fuel welding, and resistance welding. Welding is used in many industries, from automotive to aerospace, and is an important part of many construction projects.