As the public ponders the nature of Metalo, business leaders received an extortion attempt for $5 million dollars.  Lois and Clark decide to follow Jimmy's lead to the Farnham circus and find a thugish culture which forces them out.  While Clark returns to the planet, Lois continues to snoop and gets captured.  Clark is recruited to deliver the ransom money in response to the extortion attempts and meets the crooks who believe knock him "unconscious".  Changing to Superman, he follows the crooks and find them heading back to the circus.   Seeing it vacant, he uses his X-ray vision to reveal the crooks delivering the ransom money and the captured Lois.  The brazen reporter snatches one of the thugs guns and opens fire on Metalo, finding him invulnerable to gunfire.

As the crooks prepare to dispose of Lois, Superman bursts on the scene,  As he makes short work of Metalo's thugs, the criminal himself grabs Lois and leaps into the sky.  Arriving in distance mountains, Metalo reveals that he is fact human, a scientist who has discovered a super-resilient metal and developed a serum that confers super-strength.  Superman arrives and the two battle, cracking open the mountain themselves.  Over a crevasse that has exposed lava deep in the Earth, Superman's blows send Metalo into the Earth, evidently for good.  As Superman takes Lois back to Metropolis, Metalo is seen waiting in the depths, quite alive and well and plotting his next move against Superman (World's Finest #6).   Subsequent activities of Metalo over the next few years are unrecorded but a rumination in 1943 by Superman listed Metalo among his greatest foes (Superman #21).

The next recorded encounter occurred in the late 1940's when Metalo returned with a new invention, a ray that sapped Superman's powers.  Using a herd of robotic elephants, he lured Superman into the open.  As the hero cleared off the rampaging artificial pachyderms, Grant blasts Superman from a hidden alleyway and makes an escape. Returning home, Superman discovers his abilities are diminished.  Shortly thereafter, Metalo appears in a new armor, upgraded with newer metals and a refined strength serum.   He battles Superman to a stand-still until the latter uses his heat vision to over-heat Metalo in his armor.  The villain flees to cool off and Superman departs to ponder his reduced powers.  He and Lois retreat to hiis mountain fortress and begun aggressively retraining his abilities.   Metalo, in the meanwhile, has been watching for days for Superman to appear and when he fails to find him, stages a robbery to draw the Kryptonian out.   Rampaging into an armored car, Metalo is ambushed by a restored Man of Steel, who quickly removes the criminal's armor.  Still empowered by the strength serum, Grant attempts to defeat Superman, assuming the hero's powers are still diminished.  To his regret, he learns that Superman is back to normal and Metalo is shortly handed over to the police (Superman Family #217).

The later activities of Metalo on Earth-Two are not recorded.