I like both Halo and Metroid, so I was excited to watch Monty Oum's kickass animated crossover between the two; power armor against power armor, orange and green against orange and green, hero of the UNSC vs hero of the Federation, there is a lot of potential here. Yet unlike many people, I was rather disappointed; I guess I'll try to articulate why.
It starts out with New Mombasa being overrun by Covenant; somber music (In Amber Clad, from Halo 2) plays over the massacre of UNSC defenders as the opening credits roll. It's a good opening that slowly eases the viewer into the first segment. After the music stops, we see the Master Chief makes his Dynamic Entrance
on a warthog and proceeds to kick the aliens' asses. This sequence is by far my favorite of the machinima; we see lots of creativity in the choreography, including a wonderful sequence where he takes down a dozen elites with a shotgun by cocking it and using it as a close-combat tool in-between blasts. The scope of the combat is way beyond the actual abilities of a Spartan, and it doesn't really feel like Halo. However, I do enjoy that it establishes that the Chief is on the same level as (the usually more powerful) Samus.
Speaking of which... Samus makes a great entrance too, falling from the sky like a meteor and unfolding from morph ball in a foreboding, powerful manner before scanning the foe before her, Metroid Prime style. With both combatants established, the true battle begins.
The battle between the Master Chief and Samus is just as awesome as expected, with both fighters showing their abilities. Samus goes through nearly everything in her Super Metroid arsenal, yet the Chief's lucky resourcefulness manages to keep him alive. My only qualm is that the battle is far too uneven, with Samus kicking the Chief's ass and suffering only one solid hit.