Most of them are empty.
Generally the best place to find them are LMOE shelters, FEMA camps and occasionally as an airdrop (i.e, you’ll find a few random crates lying in the middle of nowhere.)
Airdrops sometimes contain a few pieces of military gear if you get lucky (i.e, a few helmets and some pants.)
LMOE shelter crates don’t seem to contain much of anything, maybe some food.
FEMA ones, I’ve yet to open but I think someone said they have stuff like gasmasks and shovels.
Also there are people that don’t use a crowbar? That’s some grade-A heresy right there, bub.
Start with the mechanic profession. You don’t even need to put points into mechanics, you can start the game-- read under the hood and boom a nice pool of EXP to slaughter stuff with and the ability to craft a crowbar. Of course, you need to find some sneakers since you don’t start with footwear for some reason.