For understanding the idea the lock*key model works very well I think. I mean, it gets hard if you take into acount that most ligands don't bind covalently and attach/detach based on chemical properties that we -for simplicity's sake- call affinity. It brings in a lot of very specific kinetics that aren't usefull for understanding the basic concepts.

If OP goes deeper into biochemistry those factors will start to play a role and will be introduced bit by bit to keep it doable. A reddit post isn't really the place for that level of detail imho.