I have been watching some youtube videos lately and noticed that there are a lot of people that use their pinkie for two string "power chords" rather than their ring finger. For example, in this video (https://www.youtube.com/watch?v=3qlmFk_rkhY) I noticed that he uses his index and pinkie to play the opening notes instead of index and ring finger like I do. I have also seen some videos where Kirk Hammett does the same thing. Is there a specific reason behind this? I don't want to be doing something the wrong way. Thanks.
The thing you described in the first place is a perfect fifth, not a chord. A powerchord is a powerchord when you add your pinky. The extra string adds definition. Is it necessary? Who knows. Experiment and see for yourself!

Oh and try not too replicate Kirk's technique too much
Personally I find it easier to do quick position shifts if I finger powerchords that way, I don't know if that's necessarily the case with other people as well though.
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Most of the time I use my ring finger and would encourage others to do so as it means the pinky's available to play another note if need be, though obviously there are exceptions to the rule.

One such exception would be something like the section at 0:58 in the video below, in which you're moving power chords around on every quaver.

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Last edited by NetherSpirit at May 18, 2013,
Yeah that's what I have always done is use my index and ring finger but I just noticed in a few videos I have watched lately that some people were using their index and pinkie so I was just wondering. It always just made sense to me since the notes are two frets apart, but since I am self taught I wanted to make sure I didn't have a bad habit that I needed to fix.
I definitely prefer using pinky for 2 string powerchords - especially on the lower frets. Works better for me in for example Megadeth type riffs that move around fast. But really only for that type music, as usually you'd want to be able to access a lot more notes. I don't think it's bad but if I were to teach a friend I'd suggest the more common way with 3rd finger.