Why are group 1 elements, in the periodic table, good conductors of electricity?

Group 1 element have a low ionization energy for the ONE outer (valence) shell electron they have--a somewhat unstable or excited state in many chemical environments---which means they tend to give up that 1 outer shell electron they have more easily so that electron can be part of an electric current (note that an electric current is a flow of electrons!). A good conductor is any material---usually a metal, and this is fundamental to the concept of a metal---that can provide electrons for electric current.