[QUESTION] Power Chords(?)

Hi,

I’ve been playing electric guitar for some time but never dealt with music theory and things like that. So, I have a question. I know what power chords are but…

What are the names of the chords below? First one sounds much heavier and the second one, I saw it in Battery by Metallica.

First One

x – – –

x – – –

5 – – –

5 – – –

3 – – –

3 – – –

Second One (Reverse Power Chord?)

x – – –

x – – –

x – – –

x – – –

3 – – –

5 – – –

Third One (Double Power Chord?)

x – – –

x – – –

x – – –

7 – – –

5 – – –

3 – – –