Gases are generally considered insulators because they are poor conductors of electricity. This is because their electrons are too far apart to be able to disperse current. With this said, noble gases are the exception when used at low pressure and high voltage.
These gases consist of neon, radon, argon, xenon, helium, and krypton. Types of elements that are considered to be good conductors of electricity are generally metals like aluminum, copper, gold, and silver. Metals conduct electricity well because they are solid and can transfer current.