Rainbow - Catch the Rainbow for sure.
Blue Oyster Cult - Wings Wetted Down.
Does Iron Maiden - Hallowed Be Thy Name count as a ballad?

Nekromantheon are tremendous. Both of their albums are great. Also worth checking out are Deathhammer, who remind me of Onslaught, and Rust, who sound like their name. Rust have a Bandcamp page. Modern thrash bands who have songs about being a thrash band always make me cringe.