I was thinking about this the other day, and I was curious about what future stars will contain for their cores. If I understand correctly, the first generation stars in the early universe didn't contain (or contained significantly less) metals. As stars evolved, they contained more metals (or maybe they produced more metals?). Will future stars become more metallic as they evolve, creating new metals, or maybe even new elements? Part 2 to this question is: is this why scientists state that X matter may not exist, and that it may eventually be created through star evolution? I hope my understanding isn't off, but if it is, please let me know :) Cheers!