sweeping usually refers to the technique of sweep arpeggios that is popular with guitarists, especially those with "neo-classical" influences. the basic sweep arpeggio begins on the 5th string and, with one fluid motion, pick each string with a downward motion (but not strumming) until you reach the first string. this is sometimes followed by the reciprocal motion upwards from the first string up to the 5th. the notes played are a basic triad, and with a bit of practice its easy to get a sweep arpeggio down. there are numerous examples of this technique in metal, my favorite being in testament's enter the pit. yngwie malmsteen sounds like he would be another example, however he does not sweep. instead, he alternate picks his arpeggios. hope this helps.