Where to Find and Catch Lairon
From Pokemon Go Wiki
Lairon are found and captured in Nest and Habitat locations.
Nests
Lairon Nests are locations that consistently spawn Lairon.
Habitats
Lairon Habitats are spawn locations where Lairon 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: