ah, never mind.. finally found out how the underground works and already got a water stone.. actually that stuff is kinda cool :D!
metal coat i remember again is attachted to wild pokemon..
anyway.. if you have something else to offer for the larvitars and staryu also reply here..
You can also get Metal Coat by going to Iron Island (take the boat from Canalave) and before you enter the cave, in the house, a person will give u a metal coat... easy! ;)