Although described as "enameled wire", rectangular enameled wire is actually not coated with an enamel paint layer, nor is it coated with vitreous enamel made of molten glass powder. Modern magnet wires usually use one to four layers of polymer film insulation to provide a tough, continuous insulation layer. Magnet wire insulation film uses (in order of increasing temperature range) polyvinyl formal, polyurethane, polyamide, polyester, polyester-polyimide, polyamide-polyimide and polyimide. Polyimide insulated magnet wire can work at temperatures up to 250°C. The insulation of thicker square or rectangular magnet wires is usually reinforced with high temperature polyimide or glass fiber.

The self-supporting coil is wound with at least two layers of coated metal wire, the outermost layer is thermoplastic, which can bond the turns together when heated. Other types of insulating materials, such as varnished glass fiber yarn, aramid paper, kraft paper, mica and polyester film, are also widely used in various applications around the world, such as transformers and reactors. In the audio field, you can find silver wires and various other insulators such as cotton and polytetrafluoroethylene. Older insulating materials include cotton, paper or silk, but these insulating materials are only suitable for low temperature applications.

For ease of manufacture, some low-temperature grade magnet wires have an insulating layer, which can be removed by welding heat. This means that the electrical connection at the end can be made without peeling the insulating layer. CCA wire is also popular because of the high conductivity of copper and aluminum, and copper provides additional strength to aluminum wire.