the first time i ever encountered modding was watching a failboat video on a hat in time. the idea that you could just take a game and add whatever you wanted was so cool to me... although unfortunately i only had a hat in time on switch so could not experience it firsthand.
blue fire was the first game i ever got on steam and i really wanted to see if i could mod it. the experience is recorded in the modding section of the blue fire shrine and was so magical
for editing models and replacing them you'll probably end up learning blender. i would never have been able to make 3D art otherwise which i love doing.
modding will probably lead you to start coding too. i ended up learning c# coding just so i could procedurally edit unreal assets with UAssetAPI which i would never have otherwise done. i eventually used it to make the blue fire rando and from there i learnt rust which also has a similar api in which i made stove... although uassetapi does have better compatibility which is slightly annoying
for even more advanced modding, reverse engineering is necessary to modify existing systems which is a very useful tool for studying how other developers solve problems. it also solidifies understanding of how memory and programs work - super important stuff for optimisation
level design is another very tricky skill to master and modding really allows you to experiment with it. without the pressure of creating your character controller you can focus on just making good levels.
modding can equip you to go on and make something even greater. it's essentially a gateway drug to game development.
one of the coolest things that mods can do is to expand on a game
even quality of life tweaks can add so much - i recently heard about movement plus, a mod for bomb rush cyberfunk which overhauls the physics of moving around the world and everyone says it's essentially the most fun way to play.
new levels and area expansions are so cool! they can add some depth to the world, challenge you, extend the storyline! rainworld custom regions are the gold standard for these as they will often add more to the rich lore of the game through environmental storytelling. not just that, but some are just straight up more gorgeous than some of the main game's regions. my favourites which epitomise this are undersea, concealed garden and the mast.
game modes are amazing and can drastically bump up how much you play. randomisers and online multiplayer mods essentially make their games infinitely replayable. i've had people tell me the pseudoregalia rando has given them 200 more hours in the game and the mario odyssey online mod has created an explosion of hide and seek youtube videos.
ultimately, expansions allow you to play more of the games you love for longer and in new ways which is beautiful
you can absolutely wreck games with mods
what if the final boss was shrek? what if you sliced foes open with deadly bananas? what if hat kid stole the declaration of independence? ...okay that last one actually slaps
you can just make the most stupid shit and laugh your ass off it's great