Alloy is a metal that has a mixture component in it.

Meaning:
At least two different metal fused together or sometimes one metal and a non metal together.
I believe it's the case of steel which contain carbon etc...
Like brass is a mixture of zinc and copper and pot metal is a mixture of all kinds of metal left over from refineries and it turned out to be a cheap alternative to casting before Urethane plastics took over.
I learned all this in automotive school back in the days but I forgot a lot, lol.

 

Please forgive this newb and don't eat me alive, but what is the underhoid insulator? Is it the padding underneath the hood?

 

That's right it is the padding attached to the hood with plastic pins.