The chord or technique is used in the songs "Wake Up Dead", "Holy Wars... The Punishment Due" and "Ride the Lightning".
The two power chords may be played in succession without shifting, making it easier and quicker, and thus avoiding string noise. The normal fingering would be for both chords, requiring a simultaneous shift and string change. Note that the two power chords are a major third apart, if the first chord is the tonic the second is the minor submediant. The spider chord fingering also allows access to a major seventh chord without the third.
The spider chord requires the player to use all four fingers of the left hand, thus its name. This technique then allows you to run down the neck playing either of the two chords
I broke my finger while trying to learn the Spider Chord.