That's quite the insightful question for your first post typhoonikan.
The Silmarillion: Quenta Silmarillion (The History of the Silmarils) - Chapter XIX: Of Beren and Lúthien
Then they [Thorondor and his vassals]
lifted up Lúthien and Beren from the earth, and bore them aloft into the clouds. Below them suddenly thunder rolled, lightnings leaped upward, and the mountains quaked. Fire and smoke belched from Thangorodrim, and flaming bolts were hurled far abroad, falling ruinous upon the lands; and the Noldor in Hithlum trembled.
It appears that
Morgoth may not just have been mad; but livid, furious...
The second part of your question is a little difficult to explain within the confines of
The Silmarillion.
The History of Middle-earth X: Morgoth's Ring - Myths Transformed: VII (iii)
The war [the War of Wrath]
was successful, and ruin was limited to the small (if beautiful) region of Beleriand. Morgoth was thus actually made captive in physical form, and in that form taken as a mere criminal to Aman and delivered to Námo Mandos as judge - and executioner. He was judged, and eventually taken out of the Blessed Realm and executed: that is killed like one of the Incarnates. It was then made plain (though it must have been understood beforehand by Manwë and Námo) that, though he had 'disseminated' his power (his evil and possessive and rebellious will) far and wide into the matter of Arda, he had lost direct control of this, and all that 'he', as a surviving remnant of integral being, retained as 'himself' and under control was the terribly shrunken and reduced spirit that inhabited his self-imposed (but now beloved) body.
The History of Middle-earth X: Morgoth's Ring - Myths Transformed: VII (i)
To gain domination over Arda, Morgoth had let most of his being pass into the physical constituents of the Earth - hence all things that were born on Earth and lived on and by it, beasts or plants or incarnate spirits, were liable to be 'stained'. Morgoth at the time of the War of the Jewels had become permanently 'incarnate': for this reason he was afraid, and waged the war almost entirely by means of devices, or of subordinates and dominated creatures.
To manifest a firm stranglehold over Arda,
Melkor was compelled to disperse his own being into the flesh of Arda - the Earth itself. This is how the
Orcs are wrought into being through the adulteration, corruption and perversion of
Elves, and perhaps even
Men. Melkor then devises
Dragons and
Wolves, such as Carcaroth, as agents of his will to do his bidding. Through the squandering of his own being into his thralls Melkor becomes physically bound to Arda and cannot assume the natural form of the
Ainur. He eventually becomes imprisoned in the flesh he clothed himself in. As a result Melkor can be slain; he knows this and is deftly afraid of it. This is why he wages war through his slaves, and why he is always devising newer and more terrible devices to achieve his own ends. We see many examples in
The Silmarillion itself:
The Silmarillion: Quenta Silmarillion (The History of the Silmarils) - Chapter IX: Of the Flight of the Noldor
But Ungoliant had grown great, and he less by the power that had gone out of him...
The Silmarillion: Quenta Silmarillion (The History of the Silmarils) - Chapter XIX: Of Beren and Lúthien
Then Morgoth recalled the doom of Huan, and he chose one from among the whelps of the race of Drauglin; and he fed him with his own hand upon living flesh, and put his power in him. Swiftly the wolf grew, until he could creep into no den, but lay huge and hungry before the feet of Morgoth. There the fire and anguish of hell entered into him, and he became filled with a devouring spirit, tormented, terrible, and strong. Carcaroth, the Red Maw, he was named in the tales of those days, and Anfauglir, the Jaws of Thirst.
The Children of Húrin - Chapter XIV: The Journey of Morwen and Niënor
And there right before her was the great head of Glaurung, who had even crept up from the other side; and before she was aware her eyes had looked into the fell spirit of his eyes, and they were terrible, being filled with the fell spirit of Morgoth, his master.
As can be seen, there's a myriad of instances where there are descriptions of Morgoth expending his own inherent being into the spirits and the flesh of his agents. This is why the battle with
Fingolfin is the last time that Morgoth came personally to battle:
The Silmarillion: Quenta Silmarillion (The History of the Silmarils) - Chapter XIX: Of Beren and Lúthien
Thus he [Fingolfin]
came alone to Angband's gates, and he sounded his horn, and smote once more upon the brazen doors, and challenged Morgoth to come forth in single combat. And Morgoth came.
That was the last time in those wars that he passed the doors of his stronghold, and it is said that he took not the challenge willingly; for though his might was greatest of all things in the world, alone of the Valar he knew fear.
Short answer: Morgoth was afraid of being slain. And his fears were justified. This is why Carcaroth, being filled with the spirit and power of Morgoth, assumably retrieved the Silmaril for Morgoth; but the Silmaril seared the flesh of Carcaroth and sent him insane.
Cheers,
Úlairi.
