Well, I don't play Metroid, but this was a bit confusing to me. The animation and art are fantastic, the artstyle especially reminds me of Samurai Jack at times. The fight an cuts do too. However, I feel like the way every shot ended with a fade out was a bit weird, made the whole thing feel disjointed. Like one moment Samus is walking, the next she's gettin assaulted by a Metroid? The uhhhh... spaghetti-O's thrown at hwr could have been shown with her dodging them from the start instead of a couple of shots of just them, cause I didn't realize what they were at first. The ending is also really abrupt. So I'm not sure what exactly transpired here and in what order. I did like the contrasted shots of her getting attacked and her making friends with the Metroid. The sound was also pretty great, very fitting.
So do keep it up, this looked beautiful and had some great potential, just maybe work on editing and story flow, making stuff clearer. Take this with a grain of salt, though, as it could be that someone who has played Metroid understands this perfectly.