The official Pokémon website has announced that Gigantamax versions of Machamp, Gengar, and Snorlax will be available in the Wild Area in Pokémon Sword and Shield from Sunday, March 8, 2020, at 5:00 p.m. PDT until Wednesday, March 25, 2020, at 4:59 p.m. PDT.

Get Gigantamax versions of Machamp, Gengar, and Snorlax in Pokémon Sword and Pokémon Shield

Head into the Wild Area to take on some powerful Gigantamax Pokémon.

From Sunday, March 8, 2020, at 5:00 p.m. PDT until Wednesday, March 25, 2020, at 4:59 p.m. PDT, Pokémon Sword and Pokémon Shield players will be more likely to encounter Gigantamax Machamp and Gigantamax Gengar in Max Raid Battles. Additionally, Gigantamax Snorlax will return to Max Raid Battles during this time as well, so take this opportunity to challenge and catch it.

To challenge these Pokémon in a Max Raid Battle, you'll need to connect your Nintendo Switch system to the internet. Then, whenever you see a pillar of light shining from a Pokémon Den in the Wild Area, you can walk up to the Pokémon Den and interact with it to start a Max Raid Battle with a Dynamax Pokémon. In extremely rare cases, a Gigantamax Pokémon can appear instead of a Dynamax Pokémon.

To get some valuable advice for tackling these challenging matches, be sure to read our Pokémon Sword and Pokémon Shield Max Raid Battle Tips article. And remember—Gigantamax Machamp, Gigantamax Gengar, and Gigantamax Snorlax will only be appearing in Max Raid Battles until March 25, 2020. Don't miss out on your chance to catch them!

Source: https://www.pokemon.com/us/pokemon-news/get-gigantamax-versions-of-machamp-gengar-and-snorlax-in-pokemon-sword-and-pokemon-shield/