yes you do in fact you need it to get most of the legendary pokemon.
You need to have the move rock climb
The Protector is one of the many items in Mt. Mortar, but you need Rock Climb to reach it.
You get rock climb at the one of the gyms
You have to beat the elite four then go to Kanto and beat all of their gyms to use rock climb.
Moltres is in the room in Mt. Silver that is furthest in the back of the first room. You need surf, waterfall, and rock climb.
you can get rock climb from beating blue i think.
Red is at the top of Mount Silver, you need to use the HM Rock Climb to get all the way up to him.
Rock climb
have a Pokemon who knows rock climb and rock smash
rock climb
In the Cerulean Cave, you can find it on BF1 in the north-east corner. You will need Rock Climb.
You have to beat all 16 gym leaders to get rock climb I believe.