Why is copper a good conductor? To answer this question, you should learn something about atoms and electrons.
As with any other creation found on Earth, copper is made up of atoms. In every atom, the outer part of the atom contain free-flowing electrons. When these free-flowing electrons come in contact with other atoms, these atoms join in the “free flow” of the electrons. As all of these atoms/electrons flow together, and bring even more atoms to the flow. With copper, these electrons detach so easily that the “flow” is created, and moves very quickly and easily.
Electrons are a negative force as opposed to protons which are a positive force. IF you were to place terminals at the end of a wire of copper that were positive and negative, the electrons would pull towards the positive force because negative and positive energies are drawn to each other through an external electric force.
Copper allows for electrons to flow smoothly and easily. This is what makes copper such a good conductor. I am by no means a scientist so you may want to check out the following video that may help explain better what I just tried to explain.