Conductors and Insulators
Insulators: materials with a high resistance to electricity. These materials have atoms with tightly bound electrons, so the electrons are less likely to jump around and form a current. Common insulators include plastic, rubber, ceramics and fiberglass.
Anything can be a conductor–even a typically insulative material–at a high enough voltage or in just the right conditions. Watch out for conditions that may reduce resistance. Always be alert for potential paths to ground, and keep yourself as well as tools and equipment far away from them.