I may be the odd one out, but if you’ve only been playing guitar for four years you may want to check some things first with your ambition so you don’t get frustrated on yourself and give up. I hate to say it but, a reality check, if you will.
MIA was written after Syn had been playing guitar for roughly ten years, give or take. Afterlife roughly twelve. You’ve been playing for four. Also, please remember this: Syn had a LOT of training before he wrote those solos. We’re talking about a guy who learned techniques, scales and theories and took them VERY seriously from the start from well-renowned sources. So unfortunately, I hate to be the bearer of bad news but it’s going to take you some preparation first before you can tackle these solos properly.
Your situation reminds me of when I heard ‘Eruption’ by Eddie Van Halen and I immediately tried to learn it after only playing lead for a year. Here I was hunched over sheet music for hours on end for a year straight and I couldn’t figure out how to make ANYTHING work. Why? He was doing techniques I didn’t know how to do properly and scale positions I wasn’t aware of that had I BEEN trained with these things, it would have made my life a hell of a lot easier.
Now maybe you DO know all the things that it takes to learn and play those solos. I shouldn’t discredit what you know and what you don’t know. But those solos are really intense and very fast and grueling. So before you jump right into a pool of disappointment and you don’t think you’re good enough, I’d strongly encourage you to really dissect the solos FIRST and see what kind of techniques and scales you should learn. I can also tell you this, if you want to learn ANY Synyster Gates solo, get proficient with chromatic scales because he uses them a LOT.
If you make sure you have the proper techniques down, it’ll make your journey of learning these solos a lot easier. Another example was with me on the Hail To The King solo. I’ve been working on that solo for two years and got stuck in a rut on a spot. It wasn’t until I actually watched him live a lot and noticed he was doing economy picking that I decided to change from alternate to economy. After practicing it this way for only a few hours my speed and accuracy went through the roof!
My final advice would be this: Take the advice of everyone else above as far as ACTION goes. Use the metronome, start off slow, take it section by section, etc. But also be kind to yourself. Make sure you know what you’re doing so you don’t overwhelm yourself and make it harder than it has to be. And because of the time gap between you and Syn of how long he was playing before he wrote those solos, give yourself time. Start off slow and let it STAY slow for months. Let yourself get the technique RIGHT with good vibratos and timing. I love it when people are ambitious, but make sure you prep yourself before the huge task so you don’t wind up in a pool of discouragement. You can do anything if you’re patient and you put the correct practice and time in. As far as solos to learn go to build up to these solos, don’t limit yourself to Avenged Sevenfold covers because most of them are pretty challenging. You have levels of ‘easy’ to then ‘holy fuck insane guitar God’ level. There’s not a whole lot of in between. But I would suggest Nightmare, Hail To The King and This Means War for some challenging builders. Good luck!