"Doom in the Heartland!"
This issue crosses over into Doom Patrol (Vol 2) #10. Page 7 of Superman #20 continues to page 20 of Doom Patrol #10 through page 22 and then back to page 7 of Superman #20.
Metallo returns, looking for an upgrade.
Paul Kupperberg is credited in this issue for his contributions in the way of "Kibitzing".