To get HM04 Strength in Pokémon Emerald, you'll need to find the Rock Smash ability and earn the Dynamo badge. You can get Rock Smash in Mauville City, the same location that you can earn the Dynamo badge. once you can use Rock Smash, you can get Strength by clearing the rocks in Rusturf tunnel. read more
You should remember the rusturf tunnel and the guy begging to see wanda.Well,if you use rock smash and clear the path,the digger guy will give you strength in return for returning the love couple together.Go to Verdanturf Town and enter the cave.There will be two rock's.A boy & a girl in the opposite sides of the rock.In your side is a boy.Use 'Rock Smash' to smash the rock.Then the boy will give you the HM Strength. read more
You can get HM04 Strength once you destroy one of the rocks in the Rusturf Tunnel. The guy will give it to you as a thank you. read more