what are the "metal models" to understand bitcoin?
Not the easiest question. Cryptocurrencies like bitcoin span different fields of study: finance, encryption, software, history, et cetera. All of which could be necessary to put it into perspective.
Fiat currencies of past eras were backed by gold. Bitcoin is backed by enormous amounts of processing power from crypto miners, encryption standards, integrity of its algorithms and respectable quantities of electricity. That could be the missing link behind the "bitcoin creates money out of thin air" claim not holding up under scrutiny. Bitcoin is intrinsically backed to a degree, although not by a traditional form of collateral like gold or precious metals.
The revolutionary "trust less" design of bitcoin, eliminates many middle men who are necessary in traditional finance, which relies heavily on a "trust" based format.
In business we have similar examples of a shift towards "trust less" design. Walmart eliminating middle man to make its supply and distribution chains more efficient, represents a quantum leap allowing them to compete successfully against sears, sams club and other retailers. Amazon took this a step forward by eliminating physical locations entirely.
Bitcoin's "trust less" design reduces human labor necessary for traditional financial institutions to operate. Which translates to a reduction in fees and costs.
This is just off the top of my head. Rambling. A good overview of bitcoin mental models would probably be much better than this short post.