Truck is in poor shape but got it cheap. Engine makes a light metallic tapping noise that increases with engine speed. It starts and runs OK, just somewhat annoying hearing the tapping. It almost sounds like it is coming from the top end, maybe from the valve area.

What things could cause this noise?

 

Worn, tired lifters and rods. Or possibly a worn oil pump. Is the engine still making good oil pressure?

 

Oil pressure seems to be good according to the gauge.
I took a short video maybe this will help.