Hidden Machine

Hidden Machines, abbreviated as HMs and also known as Secret Machines, are items shaped like VCDs or DVDs. In addition to what Technical Machines do — teaching Pokémon certain attacks anytime the player wants, they also grant important functions outside of battles such that players cannot complete the game without them. They have been reusable from the very first day they were introduced, and these attacks cannot be forgotten by normal means. 5 HMs are available in Roria.

Instruction
The procedure of using a HM is identical to how a TM is deployed — simply open the bag, click on "TMs/HMs", choose a HM and press "Use". Click on a compatible Pokémon (which will be listed as "Able") to teach that Pokémon the move. Pokémon which cannot learn the attack are listed as "Unable" in red, and Pokémon which have already learnt the attack are listed as "Learned" in blue.

The remaining process is similar to how a Pokémon learns attacks upon levelling up — the Pokémon will have to delete a move to make room if it already possesses 4 moves. However, once learnt, Pokémon cannot forget the move unless taken to the Move Deleter in Colosseum Marketplace. Thus it is not recommended to let the player's main Pokémon learn certain weak HM attacks, such as Cut and Rock Smash.

Each HM also provides an unique field usage. Some are accessed by clicking the required object, such as clicking on a small tree to use Cut, while Fly is used by accessing the Pokémon screen in menu. All HMs can be used as in-battle attacks without any restriction, but field functions are limited such that certain Gym Badges are required to unlock.

Available HMs
Here is a list of all available HMs. Field usages are in italics.

Downgraded HMs
Some of the HMs from core series have lost their status and have their field functions disabled in Pokémon Brick Bronze, because the developers deem them to be illogical, unreasonable and unnecessary, or due to the fact that they were already sacked in any main series games prior to Pokémon Sun and Moon.

Trivia

 * The introduction of Waterfall on Route 15, albeit as TM102 instead of HM5, indicates the first time in the Pokémon World that Waterfall appears before HM3 Surf.
 * This was not possible in any of the core series games prior to Pokémon Sun and Moon, because Surf must be used first before any of the waterfalls can be reached.
 * Even in Pokémon Sun and Moon where all HMs are taken down in favour of Ride Pokémon, the replacements of these 2 moves (TM94 and TM98) were awarded at the same time.