No Leaf Clover by Metallica is out of key?

[Pursuit]

Desi,

The intro to No Leaf Clover by Metallica consists of partial forms of Em (Am form) Am (Dm form) and B (E form). Only the notes on the first 3 strings are played. What key is this song in? The closest key that I can think of is the key of G (G, Am, Bm, C, D, Em). But where does the B major chord come in from? Is this a quick key change of one chord or is it something else?

[DesiSerna]

It includes the harmonic minor scale. The Em and Am are 6 and 2 from the G major scale. If the B chord was minor, then it would be the 3 chord from the key of G. But it has a D# which raises the third making it a B major chord. To play over this, raise the D notes in the scale to D#. This creates the E harmonic minor scale (E F# G A B C D#). It's identical to a E natural minor scale but with its 7th interval raised. You only do this over the B major chord. Use the natural E minor (G major) over the Em and Am chords.

The harmonic minor scale is not covered in my guitar theory course, but everything you need to know in order to get to the harmonic minor is.