2005 Chevy Tahoe Metal Shavings in Engine

Metal shavings on the magnetic oil drain plug are usually not a big consern. The fact is, every engine wears out eventually - and - every engine has (from time to time) metal shavings floating around in the oil. The good news is that your drain plug caught some of them before they did any obvious damage. As long as the shavings were not chunks, and there are no obvious oil consumption issues - smoke - or knocking - I would not be conserned. But, if the shavings are excessive and the shavings are always on the oil drain plug every time you drain the oil, then there may be something going on.

Do you ever have to add oil? If so, how much?
Does your engine smoke?
Does your engine knock?
What is the oil pressure?

It all depends on how many metal shaving were present. Yes it is normal for metal shavings to be present, but it is not normal for excessive shavings to be present. (Just for comparison) I have a 1998 Tahoe with 217000 miles on it. I got it with 110000 miles on it. I have changed the oil 23 times and every time I change my oil, there are metal shavings on the oil drain plug magnet. It does require about 1/2 of a quart of oil every 5000 miles or so, but It runs like a champ -- no smoke, no power loss.

The coolant loss issue is a very serious one. Find the leak. Sometimes coolant leaks on hot parts of the engine and evaporates - thus is cannot be seen on the ground. Start your engine and drive around for about 15 minutes - this will get your engine up to operating temperature. When you get home, shut the engine off and look very close for any sign of a coolant leak - crawl under the engine with a flashlight and look up at the front of the motor. This is where the water pump is. If the water pump is begining to fail, coolant will leak out the weep hole of the water pump. Also, smell around the engine compartment for coolant evaporating off hot engine parts.
If you are absolutely sure that there is no visable coolant leak -- then the coolant may be leaking inside of the engine and/or the transmission. The radiator has engine oil and transmission fluid coolers built into it. When these coolers fail, coolant gets into the engine oil and/or the transmission fluid. This is a VERY serious problem. The coolant can also leak into of your engine oil from failed lower intake manafold gaskets. This is also a VERY serious problem. If coolant is leaking into your engine oil and/or transmission fluid, your transmission and/or engine will fail. This could explain the metal shavings in the oil - but I hope not. Find the coolant leak immediately! Keep me posted.
Check the transmission fluid and engine oil for any sign of coolant. And check the coolant inside of the radiator for oil or tranny fluid. This will indicate a leaking radiator. If this is the condition - the radiator must be replaced and the tranny fluid and/or the engine oil must be COMPLETELY drained and replaced.