Well as the title says and as i am a beginer what would be the best song to learn...

I am into

-Guns N Roses
-Anything metal basically
I wouldnt mind learning other sorts as well
even though they suck,
green day songs are good to practice power chords with cuz there repeated power chords and you'll get power chords down pretty quick
even though green day sucks

as for metallica and gnr
metallica - enter sandman (whole song)
gnr - don't cry (it'll take practice but helps teach alternate picking and it's a moderalty easy solo)
Metallica - Black album ,anything from there is good for your rythmn playing.
Iron Maiden - The trooper - Great solo in it to play
GNR - Thats quite a hard one ,sweet child o mine ,dont cry ,civil war and knocking on heavens door - GNR can be quite hard for beginners.
Depends what bands your into really i dont know :S
metallica - battery
Ibanez RG4EXFM1
Roland Cube 30x
Line 6 Pod X3 Live
LTD Ec-1000
Mesa/Boogie Dual Rectifier Roadster
sweet child of mine was one of my first along with back in black. it takes some persistance but its so satisfying when its right
Nirvana's entire discography >_>

Seriously though some good songs you'll be able to play in no time, and everyone knows them so you can jam in front of your friends and family.

For metal there are some really easy riffs you can learn and play even if you cant do the solos. Like metallica Seek and Destroy, Ride the Lightning, Enter Sandman, One, ect are all really simple riffs.
Black Sabbath - Paranoid, easiest song ever, and pretty easy solo, but still awesome
Metallica - Enter Sandman
Iron Maiden - The Trooper
Led Zepplin - Black Dog (yea it's not really metal, but good song)
Gun's N' Roses - Don't Cry
Some others not mentioned:

She Wolf by Megadeth (helps with chugging rhythms and its not as fast as battery)
Iron Man by Black Sabbath (you can also attempt the solo, it isnt too hard)

If you really want to improve your metal guitar technique (which is mostly alternate picking and palm muting), learn Holy Wars by Megadeth or Technical Difficulties by Racer X, minus the solos.

Both songs are fast (especially technical difficulties) with a lot of alternate picking, but use easy patterns so they aren't too hard to learn. Don't worry if you can't play them up to speed or even at 50% speed. If you can get them done well you would have an easier time playing many of the harder metal/shred stuff.
I think u should start playing Crying Machine from Steve Vai


I think the best song u should learn from the band u listed is

Metallica - Enter Sandman
Guns n Roses- Dont Cry... @ Sweet Child o Mine (can be pretty tough on the solo... but its actually really simple solo..)
Honestly, as long as you take things slow and practice hard, you shouldn't have an issue no matter what you learn.

The trick is learning to use each piece to your best overall advantage:
See if that helps.