Electric guitars usually are connected through pedal where you can get various sound effects like distortion, delay, chorus and more. In any music store you can find that will fit your needs. Other way is to assemble your own using open source project details.
Electrosmash have shared his own pedalSHIELD which mounts on top of Arduino Due.
pedalSHIELD carries the analog schematic part of picking sound and output to cube. Guitar connects to input jack where signal goes through preamplifier to Arduino ADC. Then Arduino algorithm runs selected processing algorithm and then outputs waveform through DAC. Project files and program algorithms are shared if you would like to build one or even develop it further with your own effects.