What is a precision metal fim resistor made of?

Answer 1

It's made up of a metal film, of course!

Seriously, according to a spec sheet for a particular precision metal film resistor, the metal film is made of, "a proprietary thin film nickel-chrome alloy evaporated onto a high grade substrate using a high vacuum deposition process to insure low temperature coefficients and superb stability with time and temperature. The resistors are hot molded with an exclusive high-temperature epoxy to insure maximum seal, solvent resistance and mechanical strength."

Hope that answers your question!