What could possibly be wrong with my electric guitar? How can I fix it?!

What could possibly be wrong with my electric guitar? How can I fix it?

I have an Epiphone G-310 SG, and recently, I changed the strings on it for the first time. I believe I did everything right, from going around each tuning peg 3 times and stretching out each string after tuning it. So now my guitar is tuned up and ready, but what I notice is that the action of the guitar varies from being really low on the 1st fret for every string to it getting higher when you go down the neck.

My main concern is everytime I strum the E string openly, I hear a loud rattling sound. The only time it's not present is whenever you strum it very lightly, but that's weird because everytime I strum no matter how loud on every other open string, there's no rattling.

I look around and see that the rattling is most likely due to the fact that the E string has such a low action on the first fret that whenever the string is openly strum, the vibrations make the string rapidly touch the first fret (specifically, the metal fret part).

What can I do about this?

1 week ago
I know it's not normal on mine, because I just tried a friend's electric guitar, and whenever you strum an open E string, even with some force, there are no vibrations present unless you really strum hard.

1 week ago
But I have a good bet that sanding that fret down will make the paint or the exterior color fade away, making the guitar look awkward. I didn't realize this until I attempted to clean it, black residue kept wiping off, so I left it alone.

1 week ago
2 things: The problem lies in the metal part of the fret, not the wooden one.

I can't really redo this again since my strings are now all applied onto the guitar, so I can't really take them off. Besides, this problem is only occuring recently to me.

1 week ago
Well I don't know if it was a stupid mistake, since this just started happening to me today, and all the other days I didn't notice anything wrong.

How pricey would this be to repair something like this?

sounds like the neck isnt true. locate which fret its buzzing on. take some sandpaper and sand that part of the fret down. just a little! do a little at a time until the buzzing is gone. not too much!