Gallium (element)
鎵 is a specialized character for the chemical element gallium, a metal. Its meaning is entirely tied to this single element.
鎵 is a modern coined character for gallium. It combines the metal radical 金 with 家, which likely provides the phonetic element カ.
The metal radical 金 tells you it's a metal, and the right side 家 (house) can remind you that gallium is used in some household electronics. Together they point to the metal gallium.
For カ, imagine a car made of gallium: car -> カ, and the shiny metal car is parked outside the house 家.