HMs are multiple use TMs that serve a purpose out of battle, as well as being moves for in-battle use, however, in order to use an HM's purpose out of battle, a Gym Badge is required. HM05 is:

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Trivia

  • Although the move it contains varies between generations, it has always been the only HM to teach a move that deals no damage.
  • It is also the only multiple-generation HM that is not truly required to move on.
  • HM05 is the only multiple-generation HM that is never received in a city.
  • In Diamond and Pearl, HM05 has the item sprite of a Water-type HM, even though Defog is a Flying-type move.


HM04
Hidden Machines
HM06