Pokémon Let's Go, Pikachu! and Let's Go, Eevee! include a new feature
Secret Techniques, which are essentially a replacement for HMs from previous games. A variety of Pokémon can use each Technique, which will help you remove obstacles in your way and navigate certain terrain, but do not take up a move slot.
The currently known Secret Techniques are listed below.
Cuts down large trees in the player's path. It's the equivalent of the HM Cut.
Allows the player to cross stretches of Water. It's the equivalent of the HM Surf.
Allows the player to revisit towns and cities using a contraption with balloons attached. It's the equivalent of the HM Fly.
No word yet on replacements for other HMs such as Strength or Flash, but this page will be updated as soon as we have more information.
It appears that all Secret Techniques can be used by the player's partner Pikachu or Eevee, but other Pokémon have also been shown using them, such as Lapras using Sea Skim. A full list will be shown here once the game releases.