The different styles of music that guitar can be related to.
"The rule of law -- it must be held high! And if it falls you pick it up and hold it even higher!" - Hercule Poirot

© Soul Power
There are a few things you could focus your speech on
Information about the instrument (not about how its played)
You could show some pictures of well known models (les paul, strat..). You could tell people how much some of these guitars are worth, because many people wouldn't have any idea of how expencive they are. You could explain what the pickups do, and how the sound is made.

Information about famus guitarists
This could include a sample of their playing because many people have only heard guitars play powerchords. Also you could focus on guitarists who use lespauls (or other models or brands of guitars), guitarists who are from a certain time (80's? 70's? 90's?) or maybe something else that the guitarists have in common or do 1 guitarist.

You could use a combination of these idea's or you might have thought up a new idea or have 1 from someone elses post.
Quote by thetoastinator
Bring one in and melt some faces.


start a shreddin away, make them bow at ur feet while u spill ur soul out into the open air through ur axe, make them see wat playin the guitar is all about, show 'em wat real music is(assuming ur school is filled with annoying preps)
My guitars:

Ibanez RG5EX1
Eleca Dread Acoustic
Dean ML

My FX: Line 6 Floor POD Plus

In the end, fact means nothing,
its all about perspective
oh my school is obviously filled with annoying preps, don't you worry. i cant really melt faces but I will do my darndest for sure.
A band of my very own: