My top five albums of this year so far (not in any order):
Lamb of God
Lazarus AD
DevilDriver
The Black League
Novembers Doom
I'm not aware of too many big releases besides Slayer between now and the end of the year, so unless a smaller band surprises, there may not be too many changes to that list. I know a lot of critics are going to have Mastodon on that list, but I find their music kind of boring and overrated. The Lazarus AD may need an asterix beside it, because technically the album was released a few years ago on a tiny label, and is only now seeing the light of day having been re-done and released on a bigger label. I would definitely recommend checking it out regardless.