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This question largely relies on the battle environment, and the weapons that master chief uses. The environment comes into play because of the different types of shields used by the two combatants. If there were insufficient cover, Samus would easily win, simply because her shields can take more of a beating than Chief's. Were there somewhere for him to take cover, however, he may be able to damage her with hit-and-run tactics, although Samus' Wave Beam can travel through solid matter, which would damage him if he tried to take cover. Also, due to the difference in weapon types (a missle in metroid takes out roughly 15 damage, while in halo it will usually kill in one hit,) it may be impossible to accurately predict how fast Samus' shields would be lowered. In Addition to this it also depends on what suit mechanics samus is using. normal suit mechanics would mean that she would have to collect dropped energy recharges and ammo refills like in most metroid games, whereas with other m's mechanics, she would have to take cover and activate concentration mode to restore up to four energy tanks and all of her missiles. Either way, she would have an extremely hard time restoring her shields, whereas John (Master Chief) just has to take cover and within a few seconds his shields are recharged to max. Samus does have a near complete weaponry advantage, however, in the fact that her primary weapon is a beam weapon that does not run out. Also, her power bombs are powerfull enough to vaporize a human instantly and have a very high yield, so if she drops one and John can't escape in time, his suit likely could not withstand that type of explosive blast and therefor he would die. that said, John DOES have very powerful weaponry himself such as the covenant beam rifle and the rocket launcher. He also has a larger variety of vehicles at his disposal and can more easily pilot them whereas samus must use either a neuro-link piloting system, a computer or VI within the vehicle itself, or a cockpit designed for use with her suit. Now we move on to the subject of mobility and misc upgrades/abilities. Samus has a very high mobility with features like the speed boster, morph ball, and space jump. John has lightweight materials or jetpack upgrades that provide a small mobility increase, often at the cost of defense. they both are genetically and (in the case of master chief) cybernetically enhanced, and both have been trained to fight all their lives. so they are both capable of acrobatic feats even while wearing their armor suits. neither of them can take fall damage so jumping off of cliffs poses no threat and both suits are designed to protect the wearer from hostile environments. The biggest advantage for samus would be getting master chief into a submerged (underwater) environment. her gravity suit upgrade allows her to move freely underwater and her beam weapons are not hindered therin either while master chief would have some difficulty overcoming the resistance of his surroundings and few of his weapons would work underwater. overall however, i think it would be a pretty equal match.