Trainers in Pokémon Go will have the opportunity to Mega Evolve their favorite Pokémon to make them even more powerful. Mega Evolution is how you can further enhance select Pokémon to make them stronger in battle. A Pokémon Mega Evolution is different from the standard evolution process and is a step beyond its final form.
You need to use Mega Energy, which is the energy you receive for participating in Mega Raids. A Mega Raid is different than the traditional raid system in Pokémon Go, featuring a Mega Pokémon you have to take down with your friends. The faster you take down the Mega Pokémon, the more Mega Energy you receive on your Pokémon. Once your Pokémon has enough Mega Energy, they can go through their Mega Evolution.
You can only have one Mega Evolved Pokémon at a time. Suppose you have a Pokémon in its Mega Evolution and attempt to evolve another. In that case, the first Pokémon returns to its original form.
Your Mega Evolved Pokémon can explore with you and provide beneficial buffs to your friends during several events. All trainers in a raid you participate in receive an attack boost, and any Pokémon in that raid that is the same type as your Mega Pokémon receives an additional attack boost.
Mega Pokémon won’t be available to use in the Pokémon Go battle league at launch, but that could change in the future. For now, make them your buddy and go through the process of showing them off to your friends, use them in PvE battles, raids, and take snapshots of them to send to other trainers.