Flywheel weight!

That's easy to check. Pull the inspection plate and inspect...it will make a repetitive scraping noise the increases with engine rpm. Did it just start or has it always done this?
Attaching nut(s) could be coming loose (unlikely to make this noise), or have all fallen off and the flex plate is scraping the torque converter (car woulden't move)Here are some pictures:

Here you can see the drain plug made an impression in the flex plate...you can also see that the counter weight is welded on the opposite side of the impression...



Not easy to see, but this picture shows the flex plate warped from the drain plug bveing in the way.



Here is what it did to the starter




Here is what it should look like with the drain plug protruding through the hole designed for it...