Well, I've been reading Sir Malory's book on the Arthurian legends (at least, a translation of it since it was written about six hundred years ago), and it describes Merlin as being such: He was born because the Devil impregnated a nun, making him the son of the devil. He performed magic, and on one occassion, assisted a king in committing adultery (by casting a spell on the king making him look like the woman's husband) with a Duke's wife (after the Duke was dead), which gave birth to King Arthur. He was an adviser to King Arthur, and also assisted him in many of his endeavors, and told prophecies which all came true.
What's paradoxical about Merlin is that
A) He is the son of the devil, performs magic, aids people in committing sinful acts, and tells prophecies.
B) He demanded that Arthur be baptized by the Archbishop of Canterbury, used King Uther's sin of adultery to lead the kingdom into prosperity via Arthur, enchanted the sword in the stone to guarantee that it could only be drawn by the true heir to the throne, king arthur. He saved King Arthur many times and assisted him in gathering armies. He advises Christian kings and even attends Holy Mass. He even condemned King Arthur (who committed adultery with a noble woman) and prophesied that the child of the sinful union would one day destroy King Arthur.
Also, Geoffrey of Monmouth, a bishop, wrote a book called "The Life of Merlin," and "the prophecies of Merlin." So what really confuses me is why a man who seems to do evil things like magic, be respected by clergymen? He's a really bizarre character, even in fiction, and I wonder how he has had little condemnation (at least that I can see) from the Christian world. I think the reason is that there is more to Merlin than meets the eye.
To be honest, I like Merlin and I think he's a pretty cool and interesting character. He is old, wise, and well-learned and helps King Arthur in many of his endeavors. He almost comes off in some way as God's instrument. Like God, he uses the evil of men quite often to bring about a greater good. He knew that King Uther would commit the sin of adultery, and so he allowed him to do so and was able to take Arthur for himself and give him to a family to be well-raised, and later to become one of the most famous of Christian Kings.
So yea, Merlin is a very odd character.
And as to whether or not he wore a silver plate on on his head, I highly doubt it. But then again, since he is most likely a fiction character, it can be left to the imagination. I personally always imagined him as having a large white beard and long white flowing hair and wearing long robes.