Here we have a set of exercises focused on getting you playing as fast as possible, and developing serious endurance for strenuous material. Not everybody wants or needs to play this way, but this'll be helpful for anyone that's encountered hand fatigue or feels their speed is limited.
Remember to listen to your body. If something hurts, stop!
I call this the "Full Caterpillar."
Set your metronome to a tempo you're very comfortable playing 16ths at.
I like to quickly work my way up to 16ths with sets of quarter notes, 8th notes, and 8th note triplets for a bar each, as you can see below.
Keep working your way up fret by fret until you get as high as you can reasonably play on your guitar (on an acoustic guitar, for example, you'll typically need to stop around the 13th fret). Then, start working your way back down, fret by fret, till you complete the caterpillar back on the first fret.
Once you're done, you've probably got a bit of fatigue in your hand. Shake it out, up your tempo slightly, and go again!
I like to perform this exercise 4-6 times, back to back, with the last time performed at a tempo in which error starts to creep in.
Once you've got the idea of the exercise down, feel free to practice the same thing at lower tempos with groups of 16th triplets or even 32nd notes.
Below is a modification to our "Full Caterpillar" to focus more on the pinky. You can treat this exercise much the same way as the previous one, but I find it burns the hand out much quicker, so I typically don't need to play it for very long before my hand is tired out and needs a rest!
If you're through with the above exercises, you've probably given your fretting hand a workout.
Now let's address the picking hand!
This exercise is much simpler. I want you to find the fastest tempo you can play 16th notes at on the low E, and keep it up for a minute or longer.
Follow that up by repeating the process with a power chord. The wider strumming means you'll likely need to drop the tempo a little bit.
If you made it through all that, you've probably got some muscles burning in your forearms. Good! Give yourself a rest.
Repeating these exercises occasionally over the course of weeks or months, you should find your max tempo increasing slowly and steadily. I always recommend treating a difficult song as it's own exercise, but these exercises have helped me get over some sticking points and boost my maximum speed and stamina overall.