Question

Why are some substance conductors while other are insulators

Answer 1

In a conductor, electric current can flow freely, in an insulator it cannot. Metals such as copper typify conductors, while most non-metallic solids are said to be good insulators, having extremely high resistance to the flow of charge through them. Most atoms hold on to their electrons tightly and are insulators.

Answer 2

Usually metals are good conductors and non metals are bad conductors of electricity except graphite.

So materials which are made up of metals are conductors

which are made up of non metals are insulators

Because they have high resistance