No fancy explanations here .... but if you found metal it came from somewhere and is most likely the cause of your problem. Do some inspections for damage bearings, damaged cylinder walls, etc. Most of the time when an engine looses compression "all of a sudden" it is because of a stuck ring so make sure your ring is loose in the piston groove. Regardless, a fairly quick inspection should reveal the cause of your problem and any engine guy would have to do the same to reveal the problem. Not something we can just tell you here on a forum with the info provided.