Magnezone in Pokémon GO is a later generation Pokémon which evolves from a Generation 1 Pokemon.
Magnezone evolves from Magneton (which evolves from Magnemite) when exposed to a Magnetic Lure Module. Although, the real query is how to defeat the Pokémon.
Magnezone Pokémon GO: How to Defeat Magnezone
Magnezone can be an opponent as its picked to represent the leaders of Team Rocket, so you have a real chance to face it multiple times. It's a dual-typed Pokémon with Electric and Steel as its types.
With those types, Magnezone is extremely weak to ground type moves. Earthquake can absolutely demolish Magnezone and make short work of this monster.
Pokémon GO has recently released the buddy system allowing you to interact with your favorite Pokémon. The Buddy Adventure is a major expansion to this game feature, providing a wide variety of ways for you to level up and play with your buddy. While the trailer for the new game mode did not provide any specific details as to what you'll be able to do with your buddy, a player is shown feeding his buddy Squirtle berries, petting it and battling other trainers.