I wanted to build a Legion of Doom but didn't want a cliched pick for Superman such as Luthor or Braniac (besides, I couldn't find any figures of either =P), so I decided to make my own Metallo. Inspiration came from the Metallo customs done by wyLun and 3bcustoms. I bought a NECA T-800 and a Kane figure because he happened to be the right size.
First step was to bisect both figures, which I did with JeddTheJedi's help. I followed the Figurerealm tutorial and disassembled Kane appropriately. Now, the T-800 had two different POA along the spine, so we cut it off at the base of the spine, and put the gap over the pin in Kane's lower legs, joining them with superglue. JeddTheJedi sculpted over the join with epoxy and metal wire. We only learned it tipped the CG too far forward, but careful posing avoids any falling over. Due to the two origin figures, this guy is HUGE, towering at least an inch over my Arkham Ra's al Ghul and Superman/Batman Superman figures.
Next JeddTheJedi dremelled a hole in the T-800's chest and I sacrificed a LEGO stud (with the logo dremelled off) to use as Metallo's Kryptonite "heart". After that was the painting. The motivators and the inside of Metallo's chest were painted light green to imply a Kryptonite "glow", and the epoxy was painted by silver by JeddTheJedi to blend better with the T-800. The pants were painted by yours truly with a green base and given a camouflage pattern later.
My single most extensive custom so far. I'm really quite proud of the end product, even if I do say so myself. Mad props to JeddTheJedi, as all the dremelling and sculpting was his work.