If the exterior wall of a toaster exceeds 68°C while running, it may cause a burn when touched. This is especially dangerous for those with sensitive skin, such as children or older people.
Some models are designed to keep the outer surfaces at a safe-to-touch temperature, either by the use of plastic or by insulating the walls from the toasting chamber. This is called "cool wall" technology.
Plastic-bodied toasters are less likely than metal-bodied ones to give you a burn if you accidentally touch the sides.