Amplitube Metal is an expansion pack for IK Multimedia Amplitube. With the introduction of Amplitube Custom Shop, individual amp models in this package can be purchased separately rather than as a bundle.
IKM Amplitube is a software plug-in that can be used inside a DAW, and can also be used as a stand-alone plug-in.
AT Metal brings a collection of 'high-gain' amps to Amplitube. If you are not satisfied with the amount of drive/distortion of the amps in AT, the Metal expansion pack is a no-brainer.

SUITABILITY/PERFORMANCE

I really like the amp sounds in AT Metal. However, I don't like many of the cabinet options, even though there are a lot to choose from. I almost always use the same 2-3 cabinets, which is a little bit disappointing.
I should mention though that I am not a metal guitarist. I typically play rock music so I like my amp to have a decent amount of gain, but I definitely don't take it to the extreme. Someone that plays more true 'metal' may like the cabinets better.

OVERALL OPINION

Amplitube Metal has a few unique high-gain amps compared to other software sims. The Randall Warhead and Peavey 5150 are really cool, and have a different voicing and saturation than the typical Marshall/Mesa-Boogie. The choice of the JMP100 is not the typical JCM800/900 and Plexi found in most amp sims, which is a nice addition. The Mesa-Boogie Rectifier amps sound good, but are also found in a lot of other software (Guitar Rig 5, Pod Farm 2, Pod HD, etc). I would have liked to see even more amps like Bogner (although he seems to be pretty cozy with Line 6) and more Peavey amps other than the 5150.
Since the release of Amplitube Metal, IKM has released amp sims of Soldano amps and Engl amps. If you want high-gain sound, these amps are a great way to supplement the AT Metal pack.

I play in a few death metal bands, and I consider myself a pretty solid metal guitarist. I know what to look for when it comes to metal tones, and I'm always looking for some sort of modeler that can produce those famous 5150, Recto, Savage 120, etc. tones. This modelers attempts to do those, but it fails miserably. The program works by getting an interface, plugging your guitar into that interface and plugging the interface into the computer. You then just load up the stand alone application or enable the VST in your favorite DAW. I never experienced any compatibility issues, so no problems there. The manual is probably clear, but I never read it. Everything is real simple to access and get to know, but there are a few odd things. Just mess around and you'll be able to get it in no time.

SUITABILITY/PERFORMANCE

The biggest issue with this is the tone. There are some seriously problems with what these guys think a good metal tone is. It's super scooped and totally buzzy. I have no clue how they thought that's the metal tone everybody wants. On top of that, it's very stiff and doesn't give like a normal tube amp does. This causes issues when trying to do lead lines especially. If you're constantly fighting the sim, you're not going to be able to play to your fullest potential. I didn't experience any stability issues with this like I did some of the other programs, so they at least fixed that problem. It takes up a little bit of memory, but most of today's computers should be able to handle it no problem.

OVERALL OPINION

The program is thin, buzzy and pretty sterile. It might work in some sort of grindcore or experimental hardcore punk/crust band, but there's no way I could get it to work for the type of metal that I play. It just sounded too fake and felt even worse. There are better free options out there for those that want to try them.