So I want to work on a project involving touch switch. What I want to do is place a metal pad behind plexiglass. When I placed my finger on the position of the metal pad, I want it to turn on external circuity. However, I have no idea the basics of touch button circuity. Can anyone give me a couple pointers?

 

Search for 'capacitive touch sensing'.

Here's one to get you started: http://www.silabs.com/products/mcu/capacitivesense/Pages/default.aspx