Here's why:

* Nonmetals lack free electrons: Metals are good conductors because they have free-moving electrons in their outer shells. These electrons can easily carry an electrical current. Nonmetals, on the other hand, tend to hold their electrons tightly, making them less conductive.

* Covalent bonding: Nonmetals typically form covalent bonds, where electrons are shared between atoms. This sharing makes it harder for electrons to move freely, further hindering conductivity.

Exceptions:

While most nonmetals are poor conductors, there are a few exceptions:

* Graphite: A form of carbon, is a good conductor of electricity due to the presence of delocalized electrons within its structure.

* Silicon: While technically a metalloid, silicon is a semiconductor. This means it has moderate conductivity and its electrical properties can be altered through doping.

In general, remember this:

* Metals = Good conductors

* Nonmetals = Poor conductors