Here's why:

* Electrical Conductivity: Nonmetals have a tightly bound structure where electrons are not easily free to move. This makes them poor conductors of electricity.

* Thermal Conductivity: Similarly, the tightly bound electrons in nonmetals cannot easily transfer heat energy.

Examples of Nonmetals:

* Carbon (in its diamond form): A great insulator.

* Sulfur: Used in insulators.

* Phosphorus: Used in semiconductors.

Metals, on the other hand, are excellent conductors of heat and electricity because they have loosely bound electrons that can move freely.