Our PBP group's next adventure is occuring on the metaplanes. We are going to be hunting down a Force 8 free Blood Spirit (Guardian Spirit) that we encountered on our last mission against Aztechnology and unfortunately pissed off with a Force 10 Acid Bath from an Earth Spirit disrupting it. I play the groups mage, and part of my coven will be joining us on the quest to destroy it since we figured a quest to destroy a force 8 blood spirit is going to be very very nasty. (Initiate Grade 4 retired Combat Mage/Enchanter, Initiate Grade 5 High Priestess/Enchanter)

I'm wondering how things actually work on the metaplanes.

1)I know we wont be able to Astrally Project while we are there, but can spirits go astral or are they always materialized?

2)Are spirits immune to normal weapons while on the metaplanes?

3)Does how you arrive make a difference, Astral Rift/Gate vs Projecting to the Metaplanes?

4)Can you summon spirits while in the Metaplanes? Are those spirits limited to those native to the metaplane you are on?

5)How does combat work in the metaplanes, is it astral combat, or is it more like regular combat?

1) There is no astral plane in the metaplanes, spirits are in their physical form. They are not materialized technically, as they just exist in the metaplanes, but they would use their material attributes and abilities.

2) Immunity to normal weapons is a trait of the materialization power, and since they don't use that power in the metaplanes, they would not have it, though since everything in the metaplanes is magic anyways that is largely academic. Spirits are at their most vulnerable in the metaplanes where they can be killed.

3) How you get there doesn't matter, all that matters is that you got there...though some spirits may look down at you for skipping the dweller on the threshold.

4) Sure, in fact going into the metaplanes without a spirit guide is near suicide, but note that the metaplanes is not a good place to have a reputation for mistreating spirits. Spirits have a link to whatever metaplane they come from.

5) Combat is identical to meat combat, down to your physical attributes and skills, in fact you even get copies of your equiptment in the metaplanes, though it may be altered to fit the planes theme(though it will usually maintain the same functionality and use the same skill).

I seem to recall something about Astral Projection working as normal in the Metaplanes. Might be an older edition rule though.

It does, except that everyone get's molded into the metaphor of the plane.

Yeah, I had great fun playing around with the metaphors of the various planes. One fight took place on a plane that was themed around Wuxing Magic, so all the player's assault rifles became chu ko nu's, and the street sam's hand razors became a pair of those ninja claw thingies.
Same stats and all the rest, just playing around with the look of everything.

That said I hadn't realised that bit about ItNW not working. Changes things a lot, but it's obvious now that I think about it.

Don't forget that if the GM allows it then it's always possible for the mage to bring his party along as manifestations of his own image of them, rather than them actually being there. This can be a lot of fun. In the afforementioned metaplanar quest all the players were playing the mage's image of them; since the mage was quite naive, and new to the shadows, they all appeared as these awesome grizzled bad-asses covered in scars, with stubble you could light matches on. Again, no change to stats, but they all had a real blast playing charicatures of their own characters, overacting their predominant traits. After the quest was over, only the mage remembered any of it because the other characters were all in his head.