In the past month I've really progressed my playing by forming 2 bands and jamming with them once a week. I've written about 3-4 songs in the past month based around metalcore,

However my "in the moment" song writing isn't the best and I feel like it needs to improve. I have no issue sitting down with my guitar and busting out some decent riffs I'm happy with over the course of an hour or two, generally by listening to bands I like and think, "hey that's a cool sound, what if I do something similar but do this instead of that" etc.

But I'm not very good at say jamming with the drummer "in the moment"

Does anyone have suggestions to kinda improve that? any good backing tracks maybe for say metal / metalcore or something to get me started in those terms,

I've also made decent progress in sitting down and learning the major scale and minor scale using the WWHWWWH for the major scale, and WHWWHWW for the minor scale to help increase my lead ability as well and the ability to create solos "in the moment"

I'm just looking on some further tips and advice on how to progress further from here, as I've been playing covers for the past 3 years and feel like it's time to ditch covers and start creating original work with bands.
To be honest, I'm sure if there's an easy way to teach a jam session. A jam session is just based on improvisation, and if you've been playing mostly covers. Your ability to improvise might be lacking. How long have you been playing entirely?

Here's what I would do to try and work on this:

1. Use a metronome, or free drum machine and play along with an actual beat.
2. Avoid covering songs for a while and don't write any music, just work on spontaneous riffs.
3. Try to break away from metal a bit -- Basic rock n' roll and blues are both excellent 'jam genres'.

Hope this helps. Good luck bro!
Paul Reed Smith CE-24 2005 and Santana SE with Seymour Duncan pickups.
Line 6 Amplifiers
Boss Effects and Steve Vai's Wah Pedal
Dunlop Picks and Elixir Strings .48

Improving your ear with an ear trainer like the one at miles.be is always a good thing to do. Helps you recognise the sound you want to make in your head and putting it on the fretboard. I find that I can improvise reasonably better after using the ear trainer for a while.
One thing you'll often find people on UG saying is to stop thinking in shapes, and instead think in sound. I'm sure somebody can explain it far better than I can though, but the basis is to play what you hear in your head rather than what your hands want to do instinctively such as run through a scale.
Knowing what key you're playing in helps a lot. Playing a 'bum' note becomes a lot harder to do once you know what works.
As Aeon said, learning to play what you hear in your head is a great start. Train your ear and play along with some backing tracks. There's plenty on youtube. Don't just limit yourself to one genre. You might only want to play metalcore, but you should listen to everything from bluegrass to jazz to metal to pop and listen for some new ideas you can use in your own playing. After that, it's just a matter of practice. Work on your technique and your theory so you can use more complex ideas in your improv, and work on covering up your mistakes so they seem intentional.
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Junior's usually at least a little terse, but he knows his stuff. I've always read his posts in a grouchy grandfather voice, a grouchy grandfather with a huge stiffy for alternate picking.
Besides that, he's right this time. As usual.
Improvising over existing songs or youtube backing tracks will give you new ideas. I do it all the time.

Sometimes I will just use my keyboard's hold note function, create a riff with my looper and improvise over that.