*In the Zone Of Enders storyline, Metatron is the most powerful element discovered in existence, and is usable for all kinds of applications. Metatron is also the composition for the orbital frames (mechs, called 'orbital' because of their anti-gravity capabilities, and called 'frame' because of, well, their structure), such as Jehuty and Anubis.
"Metatron is out there......somewhere in this annoyingly enormous universe of ours. The element I mean. You wanna meet the agent of God? You'll have to go to Heaven."
-me
One of the main villains, if not the main villain, in the His Dark Materials trilogy. Metatron is God's (The Authority's) Lord Regent who is looking after Heaven whilst The Authority hides away pondering deeper mysteries. Metatron wants to control human free will by destroying Original Sin. He is destroyed when Lord Asriel and Mrs Coulter team up to drag him into the abyss.
"Will felt himself searched and scoured from one end of his being to the other by some vast, brutal, and merciless intellect.
And what was more, he had a spear - he was raising it to hurl -"
Metatron attacks Will, Balthamos, and Baruch (The Amber Spyglass)