All metronomes start out the same way. The keep time, they work and then it all changes. I've had metronomes collapse after a month, some have collapsed after less than a month and there are some that keep doing the job but I hate using them because they're either too annoying sounding or the sound is too soft to play against. Here's where we discuss the top five metronomes on the market and the pros and cons of each.
You'll need to go a little deeper into music theory as you proceed. The best online resource for this is Guitar Theory Revolution. It recognises that music theory is very hard for guitarists because music theory has till now been located in the piano paradigm. The Guitar Theory Revolution overthrows the piano paradigm that is holding you back and embraces the attributes of the guitar to unpack music theory. In fact, it goes further and allows you to see that the guitar is one of the best instruments for learning theory.