oil has metal shavings in it and engine is gone?

I was told my oil have metal shavings in it and engine is gone could it be something else or do I need to replace engine making loud noise from engine.

I had drove truck on Sunday no problems then on Monday morning after sitting all night started up truck making a loud clucking noise coming from engine.

Took the truck to mechanic was told that there were metal shaving in the oil and also my oil pressure light came on. Does this mean I have to replace the whole engine or could something just be replace on the engine??