According to everything I've been taught about incandescence and black-body radiation, and some quick Googling to confirm I'm not crazy, just about everything, regardless of composition, should start glowing red at about the same temperature- 798K, the Draper point, where sufficient power in the black-body radiation curve crosses into the visible spectrum to be visible.
I have just been informed by a metallurgist friend, however, that different metals in his experience begin to glow red at wildly different temperatures; typically, just below their melting points. For example, apparently aluminum glows red at much lower temperatures than steel.
My hypothesis so far: The metals in question are far from perfect black bodies (reasonable, since most metals are shiny), and differing levels of emissivity in the low end of the visible spectrum require different temperatures to raise total emission in that range to visible levels. This, however, does not explain why there should be any connection between glow-point and melting point.
Am I close to correct? Is there another better explanation? Or is my friend simply crazy?