Refers to the fusible metal alloy used to join metal parts. Often used in technical or DIY contexts.
This wiring is joined with solder.
Flux is necessary for soldering.
soft solder
gold solder; gold alloy for fusing gold items
hard solder; silver solder
brass solder; copper-zinc brazing alloy
The kanji 鑞 is a specialized character for solder, likely of Chinese origin. The reading ろう is the on'yomi.