Steelix resemble giant iron snakes. They are a reflective, silvery gray, which reflects the sunlight making them shine slightly. They are about 30 feet long. Their body is made up of rock-like sections, some of which have massive rock spikes coming out of them. They have a massive head mainly made up of their jaw. The jaw is large and wide with sets of large square teeth inside. Along their bottom jaw are a pair of ridges (varies with gender). Their eye sockets are slightly set in, giving them good eye protection. Underneath their bottom jaw and chin, on the underside of the jaw, there are small square domes. Their heads have two long ridges going from the eyes up to the top of their heads. Their jaws also have massive ridges where they meet their skull.

The rock portions on their body start at the back of their head. There are three slightly larger sections that have the massive rock-like spikes coming out of them. The tail ends in a long sharp point, but with a blunt tip. Steelix's rock-like sections don't look perfect and can easily be mistaken for rocks, for they have many chips and scrapes all along them from fights and tunneling.