The reciprocal of resistance is conductance. The unit of conductance is the mho, which is ohm spelled backwards. Conductors, semi conductors, and insulators are important when dealing with electricity. An electric conductor is a material that can carry an electric current. Conductors have very little resistance.
Resistance occurs as the electrons move and they strike each other and the atoms, losing energy.
When this happens, more energy is needed to keep the current flowing to push the electrons through the material. This extra energy is the voltage. The energy lost when the electron hits another electron or an atom causes the material to heat up, which is why light bulbs often become very hot. If one tries to make a Lewis structure for a metal, there will not be enough valence electrons for an electron-pair bond between each adjacent atom. The valence electrons can t be localized in a bond between two atoms, but instead are delocalized and belong to the crystal a whole.