changed the oil on my 1999 buick LeSabre and found a fair amount of metal shavings on the magnet end of the drain plug, any ideas as to what this may be?

I have 170,000 miles on the engine and never has this happened before

Depends on what the shavings look like. Is it chunks, slivers, or fine particles? Chunks or slivers might be a concern, fine particles not so much. If this is the first time you have observed this you might want to get an oil analysis done. Cost is around $30.

small slivers, could it be the bearings on the connecting rod? I have changed oil twice and found the slivers of metal, i changed again after 3,000 miles and no slivers of metal.???????

I believe bearing materials are non-ferrous or non-magnetic. If it were bearings on the crank, you'd hear it by now.

I agree with Mike that it is not bearings. Dissect the used oil filter and see what is inside.