The music in itself is fine (assuming you made it yourself), but I would not recommend adding your own singing with this much autotune in it. It sounded extremely off-key.
The animation you could've done a bit better than what feels like you've been making it with Paint.

Try harder for the animation and the song portion. Maybe just make an instrumental and a visual?

There are parts of this to which I would say "admirable effort!" Other parts, however, made it frankly very difficult to sit through. I did sit through them though, on account of the fact that I think there is potential here that just needs to be developed and properly utilized.

First up, get rid of the "channel intro" sequence. Just scrap the whole thing, and go straight into the video instead. It's the most run-of-the-mill, trashy YouTube-laden thing you could possibly do. And on top of that, it clashes with the actual video in a just miserable way. It's dull, it's annoying, and it's entirely unnecessary. You don't wanna be that person.

My next biggest complaint about this is that there are entire MINUTES of this video where not a single thing happens on screen and we (the audience) are left with nothing but the beat and a still-frame. I genuinely do not understand why you didn't take those opportunities to put more animation in! Add some cool stuff going on during those parts, maybe some animation of Cuphead fighting enemies, or maybe some well-drawn stills that break the monotony, or even just... anything! Anything at all would have been better than staring at those single, unmoving frames waiting for that part of the beat to end and the next verse to arrive.

After that, we need to address the Autotune... The absolutely horrendous Autotune. Look, I understand using heavy Autotune for stylistic purposes, and believe that it can but done to good effect, but in all honesty, this ain't it. It doesn't even sound like the Autotune is set to the same key that the song is in. It's just all over the place. If you want to use heavy autotune to achieve a certain sound, I say absolutely go for it, but you MUST do it right.
While we're on the note of the audio, the vocals are also very poorly mixed. I can't say for sure, but it seems to me like you just downloaded a song and recorded your vocals over it (and I suspect you did something similar with your "channel intro"). Which isn't necessarily a bad thing if you give credit and have permission to do it, but if you're going to do it, you still need to mix your vocals properly. They are way too loud in comparison to the instrumental.

Now I've listed my biggest complaints, I'll tell you why I say the attempt is admirable. For one thing, I don't think that this video was inherently ill-conceived. The lyrics are adequate and do a good job of conveying the Cuphead story-line in a way that I think suffices as an homage to the game (which I would say is a very good game and totally deserving of fan art such as animated music videos), but if you're going to do something like this again I really think you need to hold yourself to a higher caliber. You show a lot of promise here, it just seems like you've only put in the bare minimum amount of effort to make the video exist, instead of putting in the extra work to make the video good. I truly believe that you can make something better than this, and you really have the potential to make good animations, you just really need to self-criticize your work before deciding it's done, and ask yourself "what can I do to make this better before I upload it to a place like Newgrounds?"

I wish you good luck going forward, I hope you keep at it. I know you can make something awesome if you really apply yourself.

First, the Positives:

I can recognize all the locations and characters on screen from Cuphead. They are least drawn well enough to be recognizable.

Also that chiptune music is pretty awesome. Sounds like Tim Follins.

Now The Negatives:

While the artwork does represent cuphead, it needs work on some fundamentals. Golden Age cartoon art is actually quite well constructed with it's inky rubber hose people and bouncy vibrancy with characters always bouncing to some kind of beat, despite some simplistic aspects. Here, every thing seems to be a little stiff. I have I hard time at this kind of stuff too, adding a realistic sense of weight and proportion to objects. There's other little details missing too.

The animation is kind of lack luster, and there's not enough action. Cuphead is the only character I see in this animation. When I think of cuphead, I usually think of him zipping about, somersaulting over projectiles and and zapping enemies with the rapid snapping of his fingers.

And finally the autotune. Every true and professional musician I know advises against autotune, because it is not a good substitute for vocal due to a lackluster singing ability. It can only cover it up so much. You should practice your own vocal talent with rehearsals to make sure you hit each note, pitch, tone, and key. I also noticed the lyrics don't quite fit the music because there's either not enough words to hit each note in a melodic measure, or the words are not spaced out enough to fill the measure.

I know there are some software out there that can help.

I used to use a software called "Singing Coach." It's 19.99 on amazon. I suggest it because it is a little like a toned down version of Kareoke Revolution, and it's cheap readily available. There's also "Singing Method" which is more expensive, but might be better.

Back in the day, I used to play Kareoke Revolution on the Ps2, that helped me sing a little better(I used sing really terribly, now, I'm not that good, but definitely better than as a child). A more current game called "Rock Band" has a vocal mode where you can sing a song and you are scored based on performance.