No heavy metal, just hard rock albums!
This "rule" means different things to different people, and the line between is so fuzzy and subjective that it really doesn't have much meaning. That said, here's my take based on what I would consider "hard rock":
1. Pyromania (Def Leppard)
2. Black Tiger (Y&T)
3. The Great Radio Controversy (Tesla)
4. Love at First Sting (Scorpions)
5. In Rock We Trust (Y&T)
6. Whitesnake (Whitesnake)
7. Skid Row (Skid Row)
8. 5150 (Van Halen)
9. Dusk (Badlands)
10. Triumph and Agony (Warlock)