A loop pedal is a fantastic tool for a guitarist. The pedal allows you to record in a phrase and have it playback on a loop, you can also layer records and on more advanced pedals you can even take layers in and out. I would say it is the one constant every time I practise, no matter what guitar or amp model I’m playing through, I always have a loop pedal setup.
It can be immensely helpful to practise with your timing as well. Most people aren’t interested in practising to a metronome as they don’t see the point. I get all my students to use a loop pedal at some point in their course of lessons with me, so they can see how important timing and counting is. If you’re not counting, it’s impossible to get your loops in time!
The main use I have for a loop pedal is for practise over a chord progression or riff. As a guitarist it can be quite hard to practise your soloing/lead riffs without any harmony (chords) underneath, though this can be a fun challenge to try. A loop pedal can be the perfect tool for this situation as it allows you to play your chords/riff into the pedal to quickly create your own backing track.
A loop pedal can be so much more than that though, singer-songwriters like Kate Tunstall and more recently Ed Sheeran have utilised it in a much more complex fashion to create complete songs on their own.
Recently I recorded a couple of loop pedal videos of my bands tunes, you can check one of them out in this post. Overall, I can’t recommend buying a loop pedal enough, it’s the perfect practise tool and also it’s great fun messing about to see what you can create.