Afaik the glowing color just comes from the temperature, so you just need a material that stays solid at that temperature.
The opposite explanation is, lots of stuff melts before it gets red hot. Lead for example.
So glowing has nothing directly to do with metal getting soft, its just that iron/steel is used for most things we see, so we associate that temperature point with “melting”.
Red hot != soft/melting
Afaik the glowing color just comes from the temperature, so you just need a material that stays solid at that temperature.
The opposite explanation is, lots of stuff melts before it gets red hot. Lead for example.
So glowing has nothing directly to do with metal getting soft, its just that iron/steel is used for most things we see, so we associate that temperature point with “melting”.