Watch the Tremolo Picking online guitar lesson by Chris Buono from 60 Electric Guitar Techniques You MUST Know
Flurries of single notes in rapid-fire succession can be achieved with a technique called tremolo picking. Whether it be your elbow or wrist delivering the motion, when you've built up enough dexterity this is a great way to build tension or just drop a flashy lick when the time is right. Be sure to keep your pick angled, and, well, have at it!
Looking for inspiration? That moment in "Eruption" where Eddie drops melodic nirvana on the high E string around 31 seconds in.