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Morgoth wore one body which he was unable to change during the First Age of the Sun, the last 500 years or so of the Elder Days.
Morgoth shouldn't have been able to make his body grow bigger or smaller at will.
Answering another question about Morgoth's size during hs duel with Fingolfin, various answers were given, each based on a single point. But nobody tried to explain the contradictory evidence.
There are many indications that last body was very large, many times as tall as a Human. It is said that when the Iron Crown was lying on its side Beren was barely strong enough to roll it enough to get a silmaril within reach.
Thorondor the giant eagle supposedly had a wing span of about 30 fathoms or 180 feet, and after Morgoth's duel with Fingolfin Thorondor scarred Morogth's face with his claws. Assuming that the relative sizes of Thorondor and Morgoth were about the same as the relative sizes of modern eagles and men makes Morgoth well over 100 feet tall.
In the duel with Fingolfin Morgoth's feet made sounds like thunder, implying that he weighed at least tens of tons like a large sauropod dinosaur. Morgoth's mace Grond made large chasms when it smote the earth.
Since Thorondor was able to scratch Morogoth's face it is hard to believe that Morgoth had a tiny head only about two or three feet wide. A head at least ten feet wide seems to be implied by Thorondor being able to sratch Morgoth's face.
Since Morgoth put his foot ONLY on Fingolfin's neck, Morgoth's foot should have been ONLY Human or at most bigfoot sized, and Morgoth should have been ONLY ten or twenty feet tall.
And if Morgoth was only ten or twenty feet tall Thorondor should have been able to grab Morgoth's body and carry him miles high and then drop him, killing Morgoth's last physical body and changing the history of the rest of the First age.
So what is the explanation of the seeming contradiction and what is the most plausible size estimate for Morgoth?