What I use depends on the size, it's pretty technical:
Itsy-bitsy: small magnet wire
teeny-weeny: larger magnet wire
small: small buss wire
medium: larger bus wire
large: small brass rod or tubing
very large: larger brass tubing
Somewhere in between would be differing gauges of stripped or insulated copper wire, clothes hangers, metal or plastic, and drinking straws and coffee stirs
Menards has a selection of brass rod and tubing from itsy-bitsy up to huge.