I live in a hot region , so a few things cannot be stored in my trunk bag. But still, anything made of metal , textile, or hard plastic can go there.

Also, I live in an urban area and rarely go to desolate places
Some of the things I have stored in my trunk bag :

- Pair of socks
- Shemagh
- Old pair of glasses
- Magnifying lens
- Mora knife
- Foldable saw
- Hammerhead multitool ( heavy multitool)
- cordage
- Candles ( I know they soften in the summer but will not ignite )
- Flint striker

... other stuff I can't remember

Won't put food or anything flammable.
May add a metal container like a small kettle

Oh, and beside the trunk bag , I do have my smaller companion bag which stays there most of the time (for lack of a better place to be). And when I go to my dad's home like a few days ago, I take the bigger companion bag.

My definition of "companion bag" is a bag which contain "important" items, be they are importnt for living or comfort or frequently needed. Things like : wetwipes, medical pouch, utility pouch, mutitool, bandana ..etc. Some are redundancioes and some are not.

This companion bag is with ME. If I am at home, it is near me. If I travel by car , it goes in the trunk. If I go by train, it sits beside me. But it is not an EDC bag. I do not carry it everyday to work for exampe. Work time is covered by a triangle of : stuff in the work bag , car trunk bag, and in-office cache.