The Battle of Metropolis was a one on one brawl through the city of Metropolis between Superman and Doomsday. The result of the battle literally held the fate of the Earth as if Superman failed to defeat Doomsday, the mad rampage of the creature would destroy all life on Earth. The battle was renowned for resulting in the most unimaginable thing to all beings alive: the death of Superman.
One day in Metropolis, the skies turned red and Doomsday arrived, beginning to attack and kill everything possible. As an attempt to stop the slaughter, the city of Metropolis was promptly evacuated just as Superman arrived. The two beings fought each other to unimaginable levels, with no victor in sight. The battle destroyed the entire city of Metropolis, leaving it nothing by having it be reduced to ash and rubble. Eventually, Superman had to resort to devilish tactics and kill Doomsday. With the last of his strength, the Man of Steel deposited the corpse of Doomsday in the Phantom Zone, locking it up in the deepest and darkest corner known only as the Forbidden Zone. Returning to Metropolis, Superman's strength gave out and he died.
After an undisclosed amount of time, both Superman and Doomsday were both resurrected. Upon resurrection, Superman rebuilt the city of Metropolis and had a statue built in his honour, Doomsday on the other hand began to wander around aimlessly in the Forbidden Zone, his threat neutralized. Years later, however, in order to weaken the walls of the Phantom Zone, General Zod temporarily released Doomsday. This allowed Xa-Du and Brainiac to use Doomsday to their own purposes and start what became the Battle of Earth.