Never test a system without first testing for improper shorts or grounds. All matter consists of atoms. All atoms contain electrons. There are two bands of electrons, an inner and an outer band. The free electrons travel in the outer band.
Any material containing atoms with free electrons is considered a conductor of electricity.
The more free electrons a material has, the better conductor of electricity it is. Any metal will conduct electricity. Gold, aluminum, mercury and copper are the most efficient conductors of electricity. Gold is very expensive. Aluminum is inexpensive, but has a corrosive nature.