The Lost Metal title meaning

[SpinningSky he/him]

So talking about the book title

I saw several literal interpretations looking around, and they're probably all correct to an extent.
It could refer to many actual metals, I must say there's a lot of  scarcity as god metals are the general "need" nowdays  

After I read the book I didn't really consider a literal interpretation of the title and defaulted to a more metaphoric one, this is how I read it (allow me to feel mildly poetic):

I loved, loved, Wayne’s storyline in this.
I always liked the character, I have a special place in my heart for the "church of the common man" ch. in Shadows of Self, and his arc in Lost Metal is phenomenal. 
How he becomes the hero, how it parallels the story told by his mom in the beginning, how, unlike in his mom’s story, the hero doesn’t make in the end, he dies, with those beautiful closing lines.
But the the hero of this saga actually kind of survives, because out of the two metals that made up the “alloy of law”, one still lives on, but the other is “lost”.

So to me, the Lost Metal is Wayne.

Was I the only one? 

[therunner he/him]

I am much less poetic person, so I took the Lost Metal to be Lerasium (with Atium being red herring).

However, I like this so much more! Especially tying it back to alloy of law.
So now I am on board the 'Lost Metal is Wayne' train.