The "Rock Smash" move is one of the key abilities present in Pokemon Emerald and is required in order to overcome different parts of the game. This special move will be delivered to you by a man who lives in the city of "Cyclamen City" and you will be able to use it exclusively during fights. To use the move to your liking, you will first have to defeat the gym leader Walter to get hold of the "Dynamo" medal.
Steps
Step 1. Reach the city of Cyclamipolis
In the game you will reach it after earning your second medal. To reach Ciclamipoli, take route 110 starting from the city of "Porto Selcepoli".
Step 2. Head right towards the Pokemon Market to locate the house of the man who calls himself "Rock Smash Guy"; his home is the building on the right of the Pokemon Market
After asking you to give it a new name, the man will give you the move HM06 Rock Smash.
If you have not yet obtained the "Stone" and "Punch" medals you will not be able to receive the Rock Smash move
Step 3. Teach one of your pokemon the Rock Smash move
Make sure you pick a pokemon that doesn't need to learn any other attack moves, as the Rock Smash move will be the only one he can use for the duration of the game. You can teach this move to virtually any pokemon.
Despite its name, the Rock Smash move is a "Fight" type move and not a "Rock" type move
Step 4. Defeat the City Cyclamen City Gym Leader
In order to use the Rock Smash move and shatter all the rocks scattered around the world, you need to get the Dynamo Medal, owned by the Cyclamen City Gym Leader. The pokemon used by Walter, the gym leader, are of the "Electric" type, so be prepared to use some "Earth" type pokemon.
Walter owns the following pokemon: Voltorb (Level 20), Electrike (Level 20), Magneton (Level 22) and Manectric (Level 24)
Step 5. Continue towards the town of "Mentania"
After defeating Walter, you will get the Dynamo medal. This medal, in addition to increasing the speed of your pokemon, will give you the ability to use the Rock Smash move wherever there are rocks to crush. The first place where you can try the Rock Smash move is the city of Mentania.
You can reach the town of Mentania by heading west on Route 117
Step 6. Head to the cave which is at the top of the city
The path inside the cave is blocked by two large boulders. Test the effectiveness of the Rock Smash move!
Step 7. When in front of the rock to break, press the "A" button
You will be asked to use the Rock Smash move only if the pokemon that knows it is part of your current team. The boulder will be crushed and as a reward you will get the move HM04 Strength.
You won't be able to use the Force move outside of fights until you get the next medal
Step 8. Use the Rock Smash move to access the "Burning Path" and continue the game
The Rock Smash move will be used to break the boulders on Route 112 which will take you to the Burning Path. This cavern will allow you to go around the desert and reach the city of "Brunifoglia", from where you can continue your adventure.
