Non-metals, however, hold onto the electrons in their atoms much more strongly,#tosee WHY? This makes them good insulators, preventing most forms of Charge Transfer. However, this doesn’t mean they prevent all charges from transferring through them. A charged object touching an insulator will still transfer some charge directly only the surface of the insulator, resulting in a spot of charge build-up. Furthermore, polarisation still applies to an insulator.
Good examples of insulators include wood, glass, air and purified water. (Normal water can contain dissolved ions, which can conduct charges).