This is referencing a concept BOOM3R and I came up with a few months back called the amalgam.
I will be posting a detailed description of what The Amalgam is fairly soon.

In short, the amalgam is a collection of single-celled organisms that are able to, in a way, create its own body using organic and non-organic "parts".
For example, it could take two steel bars, a door hinge, and a random muscle out of a corpse and, using itself as both a sort of glue and a primitive neural network, create a moving joint.
In reality, it would be a bit more complex then that considering, for starters, there would need to be a source nutrients/energy for the muscle(s) and for the amalgam itself.

However, If you take that concept, add bones, eyes, stomachs, brains, more muscles, sensors, cameras, sheet metal, floodlights, and plenty of other scraps, you end up with something like this. A massive beast that is horrifyingly intelligent, heavily armored, impossibly powerful, and is capable of creating more like it just by existing.
For scale, just its mouth was roughly calculated to be about 3-4 feet wide.

I'm kinda happy with how this turned out considering it was mostly made by just doodling until a creature popped in my head.