I can provide some info on this one....
ExRanger provided good information above. In my limited experience (only one house fire

), it all depends on how long, how hot, and how far away.
My house burned in 2003 after a citronella candle was knocked over on the back porch. The fire traveled up the wall and into the attic. The local FD had hoses on the fire 11 minutes after the first 911 call. The picture attached below is what was left of the kitchen when it was all done. At one point during the demolition phase the house looked normal from the street....until you opened the garage door and realized that you could see all the way through to the backyard. Very much like a movie set facade.
I only owned a few guns at the time and they were all in a Homak metal security cabinet in one of the bedroom closets. The fire got to the outside of the bedroom,
but the bedroom door was closed and the fire didn't break through. The guns were all removed when we were allowed back into the house the next day. They all were sprayed down with RemOil, but that's all I had time to do.
I finally had time to take them to my gunsmith a few weeks later. My gunsmith simply pointed to my Kimber .45 and asked "Was that with the others?" When I said yes, he told me "You have nothing to worry about. That one has rubber grips on it. If the grips didn't melt that means there's nothing wrong with the steel."
I still have all of them and they work just fine.
I now have everything in a fire rated safe with the sacrificial door seal, but I honestly don't worry about fire much. If a fire starts in the room containing the safe then it's game over and time to file an insurance claim. If it starts anywhere else, you're number 1 line of defense is simply to keep the door to the room closed. All 3 bedroom doors were closed during my fire and all 3 bedrooms survived with their contents intact. The rest of the house was a total loss.
YMMV of course. Every fire is different.