Which long-standing battle feature did Pokémon Sun and Moon remove from the main-series games?

Pokémon Sun and Moon removed Hidden Machines, commonly called HMs, from the main-series games.

For many earlier Pokémon games, HMs taught field moves such as Cut, Surf, Strength, and Fly. These moves helped players reach new areas, but an HM move could be difficult to remove and could occupy a valuable move slot on a Pokémon.

Sun and Moon replaced that system with rideable Pokémon. The player could call Pokémon such as Tauros, Lapras, and Charizard to smash obstacles, travel across water, or fly between locations without permanently teaching those field abilities to a party member.

The change was part of a broader redesign of progression in the Alola region. Sun and Moon also replaced the traditional Gym challenge with the island challenge, though standard turn-based battles and Pokémon abilities remained central to the games.