Hi had a noise in my 1998 explorer, did an oil change and found metal in the oil. any idea please

metal in the oil indicates a mechanical failure and will require a pull down to fix

Engine oil is in the crankcase of the engine covered by an oil pan so I have no idea what engine oil tank you are referring to

stop by local parts store (Autozone,Advance, etc) and have them do a free fault code test. They can print out a list of faults and clear the codes

Knocking means you're still low on oil. Try have an oil and filter change. If your engine is blown, you won't hear or feel it cause it's seized. A dying engine from oil starvation would make screeching metal to metal noise. Yours sounds more like a stuck cam follower from oil starvation.

Hi,
1. Is your oil level ok?
2. Is the noise coming from the top of the engine area? If it is, you may have excessive clearance on a valve lifter. If this is the case, you could have a hydraulic lifter stuck.
Hope this helps... Good luck!

oil pump maybe tired or bearings worn out, try more heavy grade oil, if that helps sounds like bearings, and maybe an overhaul is needed, keep oil changed reg and just drive it

it could be your wheel bearing. if it sounds like a plain at take off thats it.

does the engine make any raddle noise when you start the engine. if not may just need oil presure sensor.

there is no oil fill tube. The correct procedure is to fill the pan through the drain plug. Remove the small inner plug, with the vehicle running fill the pan until ther is a small steady stream coming out of the drain plug.

Check the oil pressure switch!