As with Scyther and Scizor, again remember that this consumes the Metal Coat item when used to evolve your Onix into Steelix, so choose wisely before you confirm it! Onix to Steelix Evolution cost ...

Location of Scizor: You won't find this guy in the wild no matter how hard you try but you can catch it's pre-evolved form Scyther in Fire Red in the Safari Zone entrace, but only a 4% chance.