Answer:
Non-metals are electronegative.
Meaning it only gains electrons in their outermost shell.
For example:
Chlorine atomic number is 17. The electrons are filled in the order of 2,8,7. So, it will try to acquire electrons. The movement of electrons is absent.
While, metals are electropositive.
Meaning it gives electrons and are free to move.
For example:
Copper atomic number is 29. Its electrons are arranged in the order 2,8,18,1. The valence one electron moves. The movement of electrons is present
Electrons need to move freely for the conduction of current. As current means the movement of electrons.
This is why non-metals are bad conductors of elrctricity.