Walk: Route 1 (10%, Only in Sun & Moon), Lush Jungle (10%), Route 5 (9%) + 1 more
Its base catch rate is 120 out of 255 (higher is easier); the catch rate calculator works out your odds with each ball. For the look, the best colour match is Nest Ball or Friend Ball.
Evolution: Caterpie → Metapod (Level 7) → Butterfree (Level 10).
Metapod in every game · Pokémon Sun, Moon, Ultra Sun & Ultra Moon interactive map (Alola)