As DRL pointed out, a bit (or a lot) of theory cannot hurt. However, when you study theory, you are often stylistically thrown into jazz (if you're interested in 7ths), or basic classical music, and it does not immediately relate in a useful way.
Still, the notion of chord as having functions, movements that you can easily identify (your ear knows them, you just have to learn the names) and of understanding the basic notion of harmonic rhythm will be extremely useful at some point; not to mention rhythm if you need some grounding there.
From a rock/metal/grunge/whatever guitar player's point of view, though (that would be mine), you might be more interested in riffs and the way they interact. Then I suggest studying modes, but applying that directly to riffs you love or wrote. If you know metal, you know phrygian, for instance.
Also, my personal advice is : play from the heart first, either alone or as a band. Then study the music that comes out, which might point to new directions, which may or may not stay in the piece. Repeat as often as necessary. Bon appétit.
For any french speaker, I'd heartily recommend "La Partition Intérieure". It's primarily aimed for jazz improvisation, but there' so much knowledge in there, and it's written to help general understanding and musical applications, so anyone will find something in there to keep these creatives juices going.