I teach you all how to make it.. Goto Daiso, buy a 2 packets of button magnets (RM5/tab), then cluster them around your oil filter...simple..they're very strong magnets.
Another source of extra strong magnets. Your busted HDD drive. Rip it part, remove the magnets and strap them round your oil filter.. Free summore, if u have busted hdd.

well magnet trap has been used even in aeronautical aircraft engine. to say it doesnt work in our modern car is also wrong, because our automatic gearbox has this magnet at the oil pan to trap the metal debris.

You maybe right.. I only give suggestion how to make on the cheap. I won't do it and neither know whether it works or not. A magnet inside the gearbox sump is commonly found and there for a purpose. Its inside, that's important.