That's called an arpeggiator. It automatically plays the notes of the chords individually in a particular pattern. It is a synth.

Sweep usually refers to a filter sweep. The simplest example of this is to slowly open up a low pass filter. It sounds like the music is in a box and then you take it out of the box.
Instead of wasting more space in this forum I'm just going to make a new post in this one since it's a question related to the song...

I've become a firm believer that learning songs by ear is one of the ways to progress musically,and so I want to cover songs. Turning pop songs for example into metal,as with the above example.

I thought I had figured it out but clearly I didn't. I've been playing with A-G-F-C-E power chords while chugging their respective root notes in between thinking "hey,this sounds good,this is awesome,I'm gonna' see if I can do something more interesting lat...."

I looked up the chords for that song,they're kind of wrong from what I've been playing,well,I was wrong appearently. I thought it sounded good but yeah,I must've been deaf when I played or is there some theory I'm missing as to why it sounded good to me?

Chords: http://www.e-chords.com/chords/bonnie-tyler/holding-out-for-a-hero
because power chords are really neutral and easy to fit in correctly. if you had tried playing triads it would have been immediately clear you were off

look at the notes in the actual chords and compare them to your power chords. for the most part you're correct (on the root note), or your power chord contains chords within the actual chord

you were probably looking for something to sound "wrong" to correct and eventually get to the right note through that, but it's unfortunately rarely that simple. if you were playing individual notes to a simple melody, you can get away with that, but chords are much more ambiguous. it's just something you learn through close listening and lots of time

you're on the right track and you're absolutely right about learning by ear - for electric guitar i believe it's the best way to learn your instrument and how it relates to music. of course, that doesn't mean it's the easiest way, but persistence will get you a long way.
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aha,okay Thanks for the reply. I never did try traids so yeah....I'm just so used to metal being mostly root and fifths with melody fills in between,or at least that's how I "picture it" right now.

I'll probably stick to what I've done till now then,but something else needs to be done to make it more interesting imo.

Thanks again,it all makes sense lol *facepalm*