An apparatus designed by the ingenious professor MacLain, whom sought to use the device as an easy means of recasting the otherwise rigid to the point of immutability artificial alloy called Adamantium. Due to becoming indestructible once it cools this often made the metal impossible to shape or forge into anything else afterward.
This device would enable its handler to make the superdense submolecular structure of said metal pliable enough to be remade even when it'd already been caste. The genocidal A.I. Ultron would assimilate the device into his latest automated body after forging it from pure Adamantium using it in new and precariously unheard of ways it's creator had no idea of. After it's years of defeat at the hands of The Avengers, Ultron would change it's tactics and fabricate an army of upgraded and prior iterations of itself while taking over Slorenia.
Incorperating both Adamantium and Secondary Adamantium into it's machinoid army while retaining it's Molecular Rearranger equipment to reshape it's infinite number of bodies in the event of being damaged or destroyed.
Iron Man would utilize one of the drones own rearranger devices to make short work of the mad machines robotic clones but had more difficulty in dealing with the prime Ultron than many of the others due to the tougher, purer adamantium chassis. He would finally taste defeat at the hands of his creator after Dr. Pym had procured some Anti-Metal from reserve Avengers member; Justice.
The next time another of these metal bending devices turned up was in the possession of Cylla of the anti-mutant hating cybernetics modification select known as the Reavers. They'd come looking to procure the body of the X-Men decedent Wolverine; whom had died on one final quest for vengeance and redemption after he'd lost his healing factor. She and their leader Donald Pierce would work to secure Logan's remains whilst the rest of the crew battle the uncanny's as a distraction.
Both grave robbers would be dismayed to find their old adversaries cadaver was not within the molten metal casting which his bones & claws'd been laced with after considerable time & effort had been taken to crack it.
The Molecular Rearranger device worked by rendering molecular variances more prone to bending and/or breaking by controlling it's ductility. Ultron took this effect to unprecedented extremes by converting solid matter which he was comprised of into raw energy (ionic energy specifically) while battling Earth's Mightiest in his sixth iteration. Beyond that, it is a useful tool in reforging otherwise unmovable elements such as solid Adamantium to make it easier to construct something out of or reconstruct it for the purpose of effecting repairs..