Not sure what's wrong with the people replying to this thread.
The fella is asking for a high gain pedal to handle Heavy Rock/Metal but the suggestions are stuffs like TOD, ZW OD (essentially an SD-1 which is essentially a TS) and a tubescreamer?
Now now, before we stray off from proper recommendations, although I admit the usage of the term 'OD' is off in the title, but rather a distortion pedal would suit better.
Your aim for a tube zone ain't so far off, it does capture the rectifier vibe and is very versatile indeed. If you want it, chances are you'll still want it despite getting a substitute. Other choices to look at? The Seventheaven by Gworx would be good; comparable to that of a pricey Tone Czar Open Haus. Otherwise a Guyatone MM-X Metal Monster can deliver huge sounding tones. A much cheaper alternative would be a Hardwire TL-2; big sounding tone at a low price.
Comes down to 4:
MI Audio Tube Zone (Boogie-in-a-box)
Gworx Seventheaven (Bogner-in-a-box? very amplike in dynamics)
Guyatone MM-X Metal Monster (straight up big tone)
Hardwire TL-2 (what the MT-2 should have been, plus steroids)