Concepts:
amplification
sustain
distortion
feedback
finger versus flat-picking playing styles
"rhythm" and "lead" (or "solo") roles
synthetic instruments (Theremin, Crackle box, etc)

Music on reserve:
Robert Johnson, Crossroads blues
Cream, Crossroads (4:14)
Hendrix, Fire (live version, Woodstock) (3:42)
Boston, More Than a Feeling
U2, With or without you (4:58)

Reading:

Grove Dictionary entry on electric guitars