I have played my fair share of songs on acoustic guitar to get a hang of guitar/rhythm playing. But when it comes to playing a riff(especially metal riffs) on electric guitar, along the album track, I suddenly sound less tight, even though I sound good when I'm not playing along with it. Are there some guidelines on how to play/practice a riff to get a good end result in the least possible time with some smart practice.
Definitely use a metronome.
This tightens things up amazingl - I've benefitted from this myself.
For me, the way it 'felt' was that bits where I was speeding up by accident felt slow, like the metronome was out of time, and opposite for parts where I was slowing down.
My problem was that I'd rush more intricate parts presumably because I put too much effort into getting them out fast enough.
I've also done this while playing drums, where the effect is REALLY noticable. There it affects the whole band: everyone else plays off the timing of the drummer. Well, they're supposed to anyway. So if the drummer is rushing fills or slowing down here and there, everyone feels it.
If a guitarist is doiung this, it just makes the music sound blurry and a bit chaotic.
Regarding getting more intricate parts in time : Try setting the metronome a bit slow, so you can get to grips with any slurring of timing that might occur, or parts where you're tempted to rush.
One key point is not just to practice like this a couple of times, but make it 'the way you practice' for quite a while, say a month or so. It takes a while to set in, a bit like a new bit of muscle memory. Then try playing without the metronome alongside a recording, and see how it compares. I bet you smile :-)
Hope this helps - good luck !
It is quite hard to objectively judge one's own playing, especially at the same time as one is playing. Try to record yourself playing the riff, in that way you probably can judge your performance more accurately.
Since it's not clear what the problem is, I can only guess that it is speed that is the problem, since you mention metal riffs. At any rate, to improve tightness, practice with a metronome. Start with tempos where you are comfortable, and increase the speed gradually. Record yourself to check for improvements.