Pokémon Go ‘Let’s Go’ event, Collection Challenge guide
The Pokémon Go “Let’s Go” event runs from March 21-29 and introduces a Collection Challenge for Meltan, and other perks.
This article references relevant content from the polygon.com website. Original article link: [https://www.polygon.com/pokemon-go-guide/23650203/lets-go-event-collection-challenge-ditto-meltan-spawns]

Pokémon Go is having a “Let’s Go” themed event that focuses on Ditto and Meltan, as part of the Rising Heroes season. The event lasts from March 21-29, and features a Collection Challenge that rewards a Meltan guaranteed.
The event features both Ditto and Meltan, changing the disguises Ditto can turn into and allowing you to use the Mystery Box to get Meltan more often. Meltan can also be shiny when picked up from a Mystery Box.
Notably, this event also includes the launch of seasonal Special Research, which will be able to be claimed until June 1. Make sure to log in and grab the research if you want it, as it won’t expire once you start it.
You can also catch Pansear, Panpour, and Pansage in the wild. This is a rarity, as the three monkey Pokémon are usually regional exclusives. Make sure to use Pinap Berries on your non-native monkey Pokémon to get more candy when catching it. (They each require 50 to evolve.)
Candy gained from transferring Pokémon during the event period is also doubled, so make sure to use that to your advantage.
Below we list out the other perks and bonuses that are part of the “Let’s Go” event.
Let’s Go Collection Challenge
Catch the following for a reward:
Reward: 5,000 XP, Meltan encounter
Pokémon Go Let’s Go event Field Research tasks
There is only one event-themed Field Research task: