I am no expert but I have seen first hand when my buddy's house burned down that every rifle in his safe that had a sock survived unscathed. Those that had no sock and were right next to those with socks had plenty of heat damage to stocks scopes and plastic parts and finish.
When he rebuilt he also socked ALL his rifles in the new safe.
As a side note, all handguns on the top shelves suffered except those stored in their boxes whether cardboard or plastic.
Rust? He never had trouble wit it.
Keep in mind this is only ONE example.