Here is the Official description for episode Upgrade the 18th episode of season nine.
BRIAN AUSTIN GREEN RETURNS AS METALLO AND CLARK IS INFECTED WITH RED KRYPTONITE – Zod (Callum Blue) continues to pose as “The Blur” and asks Lois (Erica Durance) to investigate one of Tess’ (Cassidy Freeman) secret labs. An explosion rocks the lab, and Lois is rescued by John Corben (guest star Brian Austin Green) who was a subject of multiple experiments. While investigating the explosion, Clark (Tom Welling) is exposed to red kryptonite. And infected Clark takes Zod to the Fortress. Tess turns to Chloe (Allison Mack) for help and they send in Corben to stop Clark from revealing all his secrets.
Catch Upgrade on the CW on April 16, 2010