Join a Mega Raid Battle as you normally would any other Raid and tap to defeat the Mega Raid Boss.
After you defeat the Mega Raid Boss, you will receive Mega Energy as a reward as well as an opportunity to catch the Raid Boss. The amount of Mega Energy you’ll receive from a Mega Raid Battle depends on how quickly you defeat the Raid Boss. Upon defeating a Mega Raid Boss, you’ll see a Speed stat on the summary screen, which determines how much Mega Energy you earn.
Note that, once you’ve defeated the Mega Pokémon, it will de-Mega Evolve for the Raid Boss Encounter.
Mega Legendary Raids
There are two tiers of Mega Raids: Mega Raids and Mega Legendary Raids. While Mega Raids feature powered-up Mega Pokémon, Mega Legendary Raids will feature even more powerful Mega Pokémon.
Keep in mind that Mega Legendary Pokémon are very powerful, so Mega Legendary Raids are more difficult than a standard Raid Battle or even a Mega Raid Battle. To improve your chances of defeating the Mega Legendary Raid Boss, try Mega Evolving a Pokémon in your Raid Party, inviting Friends to join you in the Mega Legendary Raid, or both!