First you need to find the HM Strength. This HM can be found on Mauville town. It is on the house on the left with a scientist watching TV. Train it to one of your Pokémon and press A button to a boulder.
Chat with our AI personalities
Well any pokemon that can use the strength tm to move that boulder out of the way unless it's a big boulder you cant move that
By moving clumps of grass in pokemon emerald.
HM04
By using the move strength.
You can't its not a move in emerald.