@Music/COMIC Nerds, I need your help !!!!!!!!

I came across an interesting video that showcases Galactus facing off against the celestials.

https://www.youtube.com/watch?v=GkYw_VWi8QY

I only really know galactus from brief bouts in the animated series and what I've read online, but I've never read comics with him.

So two questions related to that video.

What comic series and starting point story wise is that story arc from?

And for the music nerds, what theme is playing in the background as he is battling the celestials? It's has threads something happening on a grander scale, and I kind of want to dive into grander themes and story arcs (i.e. not another small ball wolverine movie - the opposite of an epic)