Where to Find and Catch Meloetta
From Pokemon Go Wiki
Meloetta are found and captured in Nest and Habitat locations.
Nests
Meloetta Nests are locations that consistently spawn Meloetta.
Habitats
Meloetta Habitats are spawn locations where Meloetta is likely to be encountered, but not guaranteed the way a Nest is.
Additional Tips and Information
Best Nests
If you know a really good nest or any of the nests above is really good, list them here: