Hollow knight is a metroid-like game in the fact that you gain powerups and a map you progress through, unlocking secrets and fighting tough bosses. It's also like castlevania, but let's not get ahead of ourselves. Basically a genre of games now.
One thing I like about hollow knight is the SOUL mechanic. When you attack enemies, you gain SOUL in a container located in the top left corner of the screen. SOUL allows the knight to heal and perform spells, which is a great idea, rather than 'kill an enemy, pick up a health pack' and allows you as the player to not get cornered in boss fights without smaller enemies to pick up healing from. (okay this is pretty much every game but... I like this better.)
Another thing is the charms. Charms are equippable abilities or add-ons to your character, and you can only have a few depending on how many notches you have and how many notches the charm costs. It's pretty interesting, and it sets itself apart from other metroidvania games, and there is a lot of charms and secret combinations you can create.
Hollow Knight feels a lot like dark souls, which is pretty funny considering dark souls is its own genre now too. What I mean by "feels like dark souls" is that when you die, you lose all of your money and a portion of your SOUL container until you retrieve your shade, like in dark souls, except the retrieval is killing an enemy that looks like the knight and has the same health and stuff. Not a big thing, just thought I would mention that.
Jumping in the game is a little hard to get used to at first, but once you understand it, you can really immerse yourself in the platforming. The jump depends on how long you press the button, but there's no float or small hover in the air after letting go, the knight just falls at the same speed. This gets very ingrained in your mind as the platforming moves are added, and it just adds together beautifully in the end.
One more thing about Hollow Knight. This Kickstarter masterpiece has a ton of NPCs that are funny and in the great artstyle that this game has. I know I say that for a lot of games, but I mean come on. Beautiful world design.
I love hollow knight. It is a very good game. In fact, I love it so much that I am currently working on reaching 112% completion, which has a 1.7 or so percent trophy rate on playstation alone. I love this game. 5 stag beetles out of 5.
The nail is a fun weapon to use, and enemies have distinct designs.