There's really nothing to this movie but fight scenes that are comedic in their brutality and groan-worthy one-liners that are held together by weirdly laconic exposition by RZA, who informs you periodically what the plot is doing. But let's be clear. There isn't really plot to this movie. It's a fabrication that exists so that characters can move from point A to point B and then throw around a lot of blood. While the movie itself has an impressive color palette (particularly the whore house, where everything is in a highly disturbing shade of pink) everything potentially emotional is flat and muted because feelings are really just there as a reason to punch someone's goddamn head off.
Near the beginning, Yen Zi (the X-blade) gets a note that reads: Your father is dead. The circumstances of this caused everyone in the theater to laugh. This is the kind of experience you have throughout the entire movie.
According to IMDB, the original cut of the movie was 4 hours long, and then it was reduced to 90 minutes. I'm forced to wonder, had it been left at the original, epic length would it:
a) have made sense
b) not been a comedy
The plot, such as it is, is fairly straightforward. I think. There are a bunch of clans, inexplicably named after animals. The Lion Clan (extra hilarious if you've ever played L5R) has a coup occur within it when
Yen Zi thinks all of this is a bad idea and tries to stop it, which means Brass Body (pro wrestler Dave Bautista) beats the snot out of him. The Blacksmith (RZA) who is incidentally the only black guy in the village, saves Yen Zi, nurses him back to health, and gets his arms chopped off for his trouble. Jack Knife (Russell Crowe), who has been hanging around chewing on the scenery and being weird, oversexed and not nearly as fabulous as Silver Lion, then saves the Blacksmith and helps him make some metal arms - and thus the movie gains its title. Together, Yen Zi, Jack, and the Blacksmith team up and kill... everyone. Basically. Well, Ultra Fabulous Lion kills Madam Blossom (Lucy Liu) as she tries to save a child for a reason none of us could figure out. Then Russell Crowe as Jack rides off into the sunset still reminding the audience that yes I am totally a British guy trust me and the Blacksmith swears off making weapons forever because violence is bad, that's why we just sat through 90 minutes of nothing but.
The martial arts scenes are fairly unimpressive. There's a lot of wire work that's all right, if you're in to wire work. See it if you want a movie that feels like it's having fun with all the tropes of bad martial arts movies. See it if you want to witness Russell Crowe hilariously sneaking around the village in disguise as obviously the only white guy in the entire county (who also has a prominent and easily identified facial scar). See it so you can witness Byron Mann in a bad wig being a fabulous bastard and Daniel Wu with hilariously overdone eyebrows. See it so you can witness Dave Bautista, with apparent seriousness answer the line "I thought all the tiger were dead!" with "Yes, because I killed them!"
I laughed more in this movie than I had in the last comedy I went to. If you're the sort of person that likes MST3K and was willing to pay real money for a ticket to Abraham Lincoln: Vampire Hunter, go for it, get some popcorn, and enjoy. If you demand that your movies do things like, I don't know, make sense, this is not for you.
If you do go, just wait until you get to the (gasp) Gemini Stance! And then imagine an entire row of students from a kung fu school laughing hysterically. Because that's exactly what happened.