Once Metatron recruited Gadreel to do his bidding, he would either stay in his office and work on his typewriter, or go to Earth. Gadreel would eventually earn his right to return to Heaven and enter Metatron's office to give out reports.
Despite his loyalties, Gadreel was convinced by Castiel to help overthrow Metatron. While Gadreel sacrificed himself to convince Hannah of the truth, Castiel sneaked into Metatron's office to locate the Angel Tablet, which Metatron was using to grant himself God-like powers. Castiel discovered the tablet inside the typewriter.
Castiel destroys the tablet, thus weakening Metatron. Metatron soon returned after killing Dean Winchester and captured Castiel. He confessed about his true intentions, unaware that Castiel was broadcasting his words to the rest of Heaven, leading the other angels to burst into the room and apprehend Metatron.