There are several methods to join materials.
Welding is a fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding is distinct from lower temperature metal-joining techniques such as brazing and soldering, which do not melt the base metal.
Riveting is a somewhat old-fashioned joining method that joins materials using rivets to fasten them together. A rivet consists of a smooth cylindrical shaft with a head on one end.
A glue is used to join two materials together.