Here's why:

* Insulators are materials that resist the flow of electric charge. This means electrons are tightly bound to their atoms and don't move freely. Examples include rubber, glass, and plastic.

* Conductors are materials that allow electric charges to move easily. Electrons are loosely bound and can flow freely. Examples include metals like copper and silver.

Important Note: Even in insulators, a *very* small amount of current can still flow. This is called leakage current.

Let me know if you have any more questions!