MacBook is all out of wack

So I just got back from basic and had my dad ship me out my Mac book, first things first I charged it and typed my password in and that didn’t work like I didn’t forget my password or anything it just wasn’t working. So I restarted my Mac and it automatically opened without a password which I was like sweet I can go into setting and reset it. Everything I tried it needed my actual password to my Mac and not my iCloud so I saw something online say that I needed to hold control R to get into I’m assuming it’s bios and I tried that it didn’t work and now I’m just infinitely logged out of my Mac book it’s still signed into my cloud and everything. I did notice the battery was in shambles when I got it so I’m thinking it could be a hardware issue and something just isn’t firing right but that doesn’t really make much sense to me. Is there any way I could reset it externally if I already know my Mac password or is it just a heap of metal now?