Metal joining refers to the process of connecting two or more metal parts together to create a single, unified structure. This can be achieved through various methods, including welding, soldering, and brazing. Each technique has its own specific applications and advantages, depending on the materials and desired strength of the joint. Welding is one of the most common methods, where heat is applied to melt the edges of the metals, allowing them to fuse together as they cool. Soldering and brazing, on the other hand, involve the use of a filler material that melts at a lower temperature than the base metals, creating a bond without melting the original pieces.