This is bad (drained diff fluid)

Pictures help

 

If it's anti seize consistency that's pretty much normal I've seen it on every drain plug I've pulled, from semi to mustang.

 

Only be concerned if there's something sticking to the magnetic plug that has a serial number on it. And if that serial number can't be traced back to an important part, then it's also a non issue.

 

Pulled these off Google so they aren't the best examples but are at least something to go off of.

Normal (looks like large pieces but its just thousands of little particles held in that shape by magnetism):


Something's failing:

 

Well how much is there just a fingertip smudge or a 1/4 cup. My grandpa did lose a rear in Chicago once and made it home to northwest Iowa by hitting the axle lock.

 

By not flushing it you left a ton of that stuff in there. It was suspended in the oil and stuck to every surface as the oil drained out.

I would drain it again and flush the axle out. I'm also a cheapskate so i would reuse that oil after filtering it.

 

I agree with Spyder. The magnet can only hold so much and the rest will settle in the bottom if it sits for a while. That's why its best to drain anything right after driving it since all the wear particles are suspended in the oil.