There are a few things that determine the amount of RAM your PC can handle.
Simplest is the amount of slots on the Mobo. It’s hard to put extra RAM into a machine if there is nowhere to plug it in.
Next is the motherboard limitation. This is mostly based on the type of RAM it takes. DDR4 has a maximum size of 64GB per DIMM and DDR5 maxes out at 512GB per DIMM
Finally and most crucially is the CPU. CPUs have onboard memory controllers these days and they can only handle the amount of RAM that they can address. This value changes from CPU to CPU so you’ll want to check the specs for the model you have.
If you go over the supported amount, the PC will likely just fail to POST and never boot. If it does boot it will just ignore the extra RAM and never actually use it.