A solder is a fusible metal alloy with a melting point or melting range of 90 to 450 °C (200 to 840 °F), used in a process called soldering where it's melted to join metallic surfaces. It is especially useful in electronics and plumbing. Alloys that melt between 180 and 190 °C are the most commonly used. The word solder comes from the Middle English word soudur, via Old French solduree and soulder, from the Latin solidare, meaning '‘to make solid’'. In North Am… (More on Solder)