HM04 (Japanese: ひでんマシン０４Secret Machine 04) is an HM introduced in Generation I. It teaches a compatible Pokémon a move that can also be used in the field; but using an HM in the field requires that the player have a certain Badge (except in Generation V). HM04 has always been Strength. For compatibility, refer to the move's page. HMs can used to teach moves without limit.
In the player's Bag from Generation II games, this is identified as H4 (Japanese: ひ4).
HMs in the Mystery Dungeon series are named only by the move they teach. For example, Cut is the item that teaches the move Cut. Most HMs, however, correspond to an HM in the core series' contemporaneous games.
HMs in Pokémon Mystery Dungeon games prior to Pokémon Super Mystery Dungeon can be used any number of times. In Pokémon Super Mystery Dungeon, "HMs" are treated like TMs and only usable once. However, if an "HM" is dropped on the ground, it has a different color than a TM.
Cut is the item that teaches the move Cut. Most HMs, however, correspond to an HM in the core series' contemporaneous games.
