Melkor era grandioso. Seu capacete, como o Morgoth, era tão pesado que Beren não conseguiu levantá-lo [Lays of Belereiand, 8,4136-4137], e ele tinha uma cicatriz e mole [12,3604-09, 3615-3617, 3632-3634]. A forma física de Melkor no começo é descrita como:
because of his mood and the malice that burned in him that form was
dark and terrible. And he descended upon Arda in power and majesty
greater than any other of the Valar, as a mountain that wades in the
sea and has it head above the clouds and is clad in ice and crowned
with smoke and fire; and the light of the eyes of Melkor was like a
flame that withers with heat and pierces with deadly cold. [Silmarillion; Ainulindalë]
Ele também disse ter andado em várias "formas de poder e medo" [Do Início dos Dias]
he put on again the form that he had worn as the tyrant of Utumno: a
dark Lord, tall and terrible. In that form he remained ever after. [Of the Darkening of Valinor]
Não superestime o tamanho do Melkor ou de qualquer dos Ainu. Há também uma outra descrição dele quando ele luta contra Fingolfin:
Morgoth came, climbing slowly from his subterranean throne, and the
rumour of his feet was like thunder underground. And he issued forth
clad in black armour; and he stood before the King like a tower,
iron-crowned, and his vast shield, sable unblazoned, cast a shadow
over him like a stormcloud...
Melkor held aloft Grond, the Hammer of the Underworld, and swung it
down like a bolt of thunder... Grond rent a mighty pit in the earth,
whence smoke and fire darted...
Morgoth bore his shield upon him. Thrice he was crushed to his
knees... Morgoth set his left foot upon his neck, and the weight of it
was like a fallen hill. Yet with his last and desperate stroke
Fingolfin hewed the foot with Ringil [The Ruin of Beleriand]
Morgoth é grande, mas não como um gigante. Quando ele colocou o pé no pescoço de Fingolfin, ele ainda podia usar o braço para balançar a espada.