I have to recommend Ascent DX - it is free, quite short, but it condenses everything I enjoy about the metroidvania genre I to a bite sized play session.

Tunic is one of the best games ever made, nevermind just in the metroidvania genre. It is good for reasons I can't tell you without spoiling some of the magic. Trust me!

Phoenotopia Awakening was stupendous fun and way bigger than I thought it would be. Strongly recommended. Typical side scrolling platforming gameplay, with emphasis on exploration and puzzles as well as the combat and platforming.

Death's Door was so damn fun, and it felt quite fresh in a way I can't describe. Its an isometric hack n slash game with some puzzle elements. Tells a cool story, and is a sequel/successor to Titan Souls, from the same devs.

AAAAXY was a lot of fun, and free and open source. Sort of like antichamber meets metroidvania. Short and sweet but also challenging!

Otherwise, as others mentioned, I can't recommend these enough!:

Hollow Knight

Ori And The Blind Forest/Will Of The Wisps