If you have had the engine running for a while you may see metal in the oil upon draining. Look for those tell tail greyish silver streaks or maybe some very small metal fragments in the drain pan. A magnet is very helpful here if you have one. Run your magnet around in the pan to see if it picks up anything. Moly prelube from the cam can look like metal in the oil so the magnet will confirm it. Unless you have a catastrophic failure such as a broken rod bolt you won't see any damage until you disassemble the entire engine and look at the bearings. Hope this help!