Morgoth was a refashioned Melkor in towering armor, but he was greatly depowered since his dissent and mainly relied on Balrogs and Dragons to win his battles. An Elite Elf, Fingolfin, managed to cause him to walk with a bit of a limp.
Originally, during his first battle with Tulkas, he carved up the countryside, reshaping the continent in that battle. That was as Melkor, the freshly fallen Valar.