How to play the Intro to Metallica Enter Sandman

Enter Sandman comes off Metallica's self titled album, often referred to as the Black Album. The song can be recognized with it's casual intro followed by a thunderous drum beat and heavy distortion. The intro is pretty straight forward and a good riff to practice since I interpret it as using an open string.

E|---------------------|
B|---------------------|
G|-------0-------------|
D|---------------------|
A|----7-----------7----|
E|-0--------6--5-------| X 12

I've seen several tabs for this song, but many use the 5th fret on the D string. I don't think that it's correct but certainly one can play it that way too. Here is why I think it's an open G string, when you listen the intro you will notice that the G note rings through out the intro. It's that simple, plus I think this way plays more naturally.