obviously noticeable metal shavings would be serious.
however any metals (inside an internal combustion engine) contacting with other moving metals will have, until seated, will have, to a very small degree, some metal micro-bits in the oil, hopefully too small for the naked eye to see.
that's what I failed to specify, minute traces!.....drop a magnet in used motor oil and pull it out and let it drain the oil off, then with a magnifying glass you might even see tiny traces of metal.
for example, on commercial engines, our mechanics sent oil samples out to have them tested for signs of bearing wear, the amount of copper (?) content in the oil would tell them a lot about engine wear.
I understand on all petro engines, the internal parts or lubed prior to assembly, or should be.
I am also with the understanding, that most modern petrol engines are run for a period of time, how long?....don't know, but for a bit at least...do they change the oil after that run?...I doubt it.
i'm gonna change my own oil at 1k and put in amsoil.