Solder is a metal or alloy that melts at a low temperature . There are two types of solder ; soft solder ( easily melting alloys that are melted with soldering irons and used for electronics and electrical work ) , and hard solder ( high melting alloys or metals that are melted with a torch ) . Solder ( or or American ) is a fusible metal alloy with a melting point or melting range of 90 t , used in a process called soldering where it is melted to join metallic surfaces .