Materials that allow electrons to flow freely are called conductors.

Here's why:

* Conductors have many free electrons that are loosely bound to their atoms. These electrons can easily move throughout the material when an electric field is applied.

* Insulators have very few free electrons, and their electrons are tightly bound to their atoms. They resist the flow of electricity.

* Semiconductors fall somewhere in between conductors and insulators. Their ability to conduct electricity can be controlled, making them useful in electronics.

Some common examples of conductors include:

* Metals (copper, silver, gold, aluminum)

* Graphite

* Saltwater

Let me know if you have any other questions!