I have no idea what their IQs are, but if Reed and Dr. Doom are around 350-400, then Metron's about 10,000. Metron's IQ is on a level with, and probably higher than, Grandmaster's. I don't see Reed or Dr. Doom as being able to out-think the Grandmaster on their best day, and from what I've seen, Metron's smarter than Grandmaster.
Metron thinks on a universal-scale; he's seen things way beyond the experience of even the smartest person (excluding "people"/near-cosmic entities like the High Evolutionary).