Truck won't go can someone help?

I have a 2015 Chevy Silverado 4 by 4 Z71 Goed go
into drive reverse neutral one but the gear won't
shift to make it go I changed my transmission fluid
and filter I did have a lot of metal in the bottom of
the pan it was like mud and fluid looked like black
Chevy kool aid but I was driving the truck and it
was running good before then all of a sudden the
check engine light came on and I was going to
stop to get something to eat and I didn't have
reverse and then when I get to my house I park it
and I go back out an hour later to go somewhere
and it won't go but makes a loud shifting noise
right after I start it.