Chief outmaneuvers Samus by a long shot, she's slowed down by her armor, the chief is much faster than her. She may hold the edge in firepower, but the chief has much more combat experience, the chief was responsible for single-handedly repelling the covenant from earth, not to mention destroying the first halo ring, stopping the covenant in halo3 (even though the arbiter has credit for killing Truth), and single-handedly killing the Didact. Samus is a mercenary, granted she can hold her own in a fight, but the Chief is much better at combat than she is. But who am I kidding, they'd meet, and then they'd bang. End of story.

Have you even played any of the Metroid series?? Samus is way faster and far more agile than Chief. Her armor doesn't weigh her down much at all. She isn't totally human either having that Chozo DNA, and has an absolute ton of battle experience. I think people pick Chief because Halo is so popular, not because they're objectively looking at their battle capabilities. If she rushes him and goes into indestructable, object destroying, wall smashing charge ball mode, his shields and armor are screwed. His normal firepower wouldn't do a whole lot to her and his heavy shit is too slow. She would blow his shield off quick and just finish him with a steady stream of rockets. That's is she didn't choose to go into ground ball form and bomb the hell out of him.

There isn't enough space between her and the chief to activate speed boost.

I agree with everything BUT the flood, you cannot kill them with fire power, as the forerunners tried.

I'm not sure what the Flood has to do with this fight? The Flood do keep coming, but it's not like you can't kill them. It's just that they're everywhere and are too hard to stop. Then again, Metroids are fairly brutal too. It's kinda hard to say what would even happen if a Metroid absorbed a Flood. The have a Hive Mind type control so they probably couldn't be taken over.