Copper is the most common form of cabling for networking. It's rated highly for conductivity and as such can conduct electricity more easily than other metals.
It's much cheaper than fiber, however, it's much slower in terms of data rates. If speed is of the essence, fiber is better for the same thickness of cable.
Being metal, interference can be an issue. Radio bursts and electromagnetic noise can degrade signal quality to the point of being unusable depending on the environment, and there's also the potential for wiretapping, unlike fiber.
Being an older standard, copper has the benefit of excellent interoperability and legacy compatibility.
An in-between option in terms of cost and performance, Coaxial or Coax is much like copper, where an electrical current transmits data. Coax has 3 main components to its cable. The first is the core, made of copper or another conductive material. This aspect works exactly as a copper wire would by sending electric pulses to encode a message. The next layer is an insulation layer to keep things contained, as well as keeping data safe from physical damage to the cable. Lastly is a shield, also made of copper. The shield doesn’t intentionally conduct current but is used to help absorb any external interference that may affect the transmitting of data. This is why we often see Coax next to antennas or transmission lines in cases where fiber may be too expensive or overrated.