Well that's it then... I thought about going to one of the Finnish fests, but don't really know how they are?
Did also hear Hellfest is cool so may look into that more seriously.
Tuska 2nd to 4th of July
Tuska is hold in Kaisaniemi park located just a few hundred meters behind the central railway station in Helsinki, so it's very convenient to come there. Good location, you can bring your own booze to the festival area in plastic bottles, pretty decent bands but the food is usually not so good.
Line-up looks pretty good so far: Devin Townsend Ziltoid The Omniscient, world exclusive, Mastodon, Megadeth, Satyricon, Testament, Kamelot, Devin Townsend Project, Finntroll, Hypocrisy, Pain, Tarot, Nile, Swallow The Sun, Overkill, Cannibal Corpse, Obituary, Bloodbath, Trigger The Bloodshed, Warmen, Sotajumala, Holy Grail, Rytmihäiriö, Torture Killer, Barren Earth, Insomnium, FM2000, [Amatory], The Arson Project
Hammer Open Air Metal Festival 11th to 12th of June
Sauna Open Air 10th to 12th of June
Nummirock 24th to 26th of June
Metal midsummer party in the middle of nowhere, you can get there by a train/bus combo though.
Jalometalli 13th to 14th of August
This is good one, great bands, both in- and outdoor stage, good food.
Other more or less rock and pop festivals with some metal bands in the line-up
Provinssirock 18th to 20th of June
Ruisrock 9th to 11th of July
Ilosaarirock 17th 18th of July
Then there's Myötätuulirock where Exodus will be this year and Ankkarock were Amon Amarth were last year.