There is no one thing you have to learn, you'll only improve your guitar playing by practising all the different techniques. i suggest either getting lessons from a qualified guitar teacher (or at the very least someone that you know who is already proficient) or checking out some of the lessons for beginners here on UG
Appreciating Metal since 1998

R.I.P - Ronnie James Dio

Chords for a start lol, when starting GET RHYTHM DOWN FIRST!
Good rhythm helps lead playing.

Many insist on Scales, if you do decide to learn some go for The Major Scale & Pentatonic Scale

That is the basics
Learn some chords, simple ones.

Then find a song you like with those chords in, if you can't find a song you like then you could make up your own song OR learn a song you dont like (we all have to do that at some point )

If you don't understand this information check out a beginner guitar lesson on youtube, we all start from the easy stuff, don't get bummed out by it
Yeah i bummed off chords when i first went off on my own
and thought i was hard strumming all the songs i could find
then i discovered the powerchord
that was a good day
I s'pose it depends what you listen to, i started off with lots of indie and soft rock in general which explains the chord bashing
I got into metal and blues in year nine which taught me how to play riffs, as well as improvise and write solos
I suppose depending how you learn you can get better at different levels
just learn about music in general you'll gradually find you way through