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Agent May is an extremely intelligent woman who presents a stoic, rather uncommunicative demeanor at all times. According to Agent Coulson, earlier in her career May was a much friendlier person, prone to playing pranks on her fellow agents and generally happier, though still rather quiet. A tragic experience while on a mission in Bahrain to contact an unregistered gifted individual left May emotionally scarred and caused her to become the rigid, somewhat withdrawn person she is today. This led to her decision to avoid field work until Coulson (he believed) persuaded her in "Pilot" to sign up with his new team.
She is frequently the pragmatist to Coulson's more humanitarian approach, for example, in "Repairs", when she tranquilizes Hannah Hutchins to ensure the situation does not escalate. May is fiercely loyal to her S.H.I.E.L.D. team and more specifically Agent Coulson, and she will do whatever it takes to keep them safe. Sometimes her methods appear harsh, but this is due to her dedication to protecting those in her charge.
May is an Asian female with brown hair and brown eyes, her height is about 5'4". When she is dressed casually, she usually wears black ankle boots, gray jeans, dark colored T-shirt and leather jacket. When in combat she wears black boots, black combat trousers and combat long sleeved top with armor.
May is extremely gifted in the field of martial arts. It was revealed in "Repairs" that May successfully defeated a girl who could corrupt with a touch, and many S.H.I.E.L.D agents single-handedly and unarmed. At some point in her career as a S.H.I.E.L.D agent, she gained the nickname "The Cavalry" and is well known throughout the agency. May exhibits abilities such as being able to seemingly vanish into thin air within seconds . She is a remarkably skilled pilot, and although leaving the field, retains her piloting license. Up to the age of 12, she was an ice skater and gave that up to pursue martial arts because the mats broke the fall rather than ice.
May used to be a field agent for S.H.I.E.L.D. and was highly skilled at her job. During her time as a field agent, she became somewhat of a legend at the agency. 
On a mission in Bahrain to make first contact with an unregistered gifted person, several of Agent May's colleagues and a young civilian girl were taken hostage by the man's followers. Agent May single-handedly stormed the building in which the hostages were being held and killed an unknown number of assailants, all while unarmed herself. She managed to free all of the hostages unharmed. However, the experiences May had on that mission, which she refused to fully disclose to Phil Coulson, left her emotionally scarred and caused a radical change in her personality.
After this mission, May attained almost legendary status within S.H.I.E.L.D. for her exploits, which earned her the nickname "The Cavalry." It was later revealed that the experience that traumatized May was that she shot an young "inhuman" girl who was controlling the mind of captured SHIELD agents .
In "Turn, Turn, Turn", May states that she put together the team, by essentially guiding Coulson to choose the people she would need, including the tech-bio combo of Fitz and Simmons and Ward as a specialist, if it became necessary to put Coulson down.
Throughout "Providence" and the early part of "The Only Light in the Darkness", May attempts to justify her actions to Coulson and rebuild at least a modicum of trust. "Phil", however, as she calls him during this endeavor, is having none of it, and by the end of the latter episode, May has struck out on her own, leaving the base and meeting up with her mother, apparently with the intention of seeking out Maria Hill. This may, however, still be part of a last-ditch, desperate effort to reconnect with Coulson. In that same episode it was revealed that she was once married.
- May: "I assembled this team!"
- Coulson: "What?"
- May: "I evaluated what was needed and gave the assessment to Fury, and he gave you the parameters for your unit."
- ―May about Coulson's team.
- Main article: Phillip "Phil" Coulson
Coulson and May go way back, since the start of Coulson's team, May was on it. They share a deep bond and often rely on each other to keep secrets. Unaware to Coulson, May was monitoring Coulson's status and reporting to Fury, she also revealed that she knew about Tahiti. Coulson relies heavily on May and understands that she does not like being in the field, he also understands that she is very dangerous. According to Garrett, May would follow Coulson to the grave. After finding out that May was reporting to Fury behind his back, Coulson was furious, his anger got to the point where he shot May with an ICER and later told her that she was no longer a friend but an ally. Later on, while Coulson still seems to struggle a little with her apparent betrayal of his trust, there are indications that loyalty and friendship has been rebuilt. She continues to be his closest confidant.
- Main article: Grant Douglas Ward
Former colleague and "friends" with benefits (from the end of The Well - the latter is not to be made public, as evidenced by the flat, angry glare she gives him at the start of "The Bridge" when, during a sparring session on The Bus, he alludes to it. He later speaks of the issue directly, saying he can 'separate Church from State'). She informed Coulson in "Seeds" of this, saying, "Agent Ward and I have been having sex…", and later confirming that he had heard her statement. It is revealed that Ward was having sex with her in order to gain her trust.
Soon they get in a fight and Melinda breaks up with him, so Ward tries to gain Agent Skye's trust. In the end, Ward is Hydra and betrays the team and Melinda. Afterwards, Melinda finds him and breaks his throat and shoots nails into his foot.
When Ward proves an ongoing thorn, even dagger, in the team's side, May regrets not terminating him during their fight, and says so repeatedly.
- Main article: Jemma Simmons
Colleague. May sees her as a 'kid' and worries about her. It is obvious that Jemma also has warm regards for May.
- Main article: Leopold "Leo" Fitz
Colleague. She has pranked him once, harmlessly ("Repairs"). Not unlike Simmons and Skye, May takes it upon herself to look out for Fitz. Her treatment of him softens slightly after his trauma.
- Main article: Daisy Johnson
Colleague. May is her Supervising Officer. Trusted but not completely, as she is an 'unknown variable'. Skye and Melinda have a special bond. Skye looks up to Melinda and feels that she is one of the only people she can trust. Skye dredges up painful issues, and provokes unwanted questions, causing May to occasionally, perhaps unintentionally, use her to vent her own frustrations. May, however, seemed more than willing to beat Ian Quinn to death with her bare fists for shooting Skye, and so it is clear that May is ferociously protective of the young agent. During the events around Jiaying's attack on SHIELD, she came to question Skye's loyalties at first, but aided her later in stopping the Inhumans.
Antoine "Trip" TriplettEdit
- Main article: Antoine "Trip" Triplett
Colleague. Seemed to have respect for one another as agents. We can infer May saw him as an ally and was saddened by his death.
- Main article: Andrew Garner
Ex-husband. They once had a warm and happy marriage, having eloped. However, after the mission in Bahrain that earned her the nickname 'The Cavalry' and left her emotionally scarred, May was afterwards unable to handle a relationship, which led to her divorce. However, it is later implied that she regrets this and may still hold feelings towards him. During her "vacation" she met up with Andrew in Maui. Afterwards her whereabouts were unknown to the team. During Garner's transition to inhuman in season 3, it becomes clear that although she still loves him, she is willing to kill him to protect her team and other Inhumans. At the end of the season, May is seen visiting him in S.H.I.E.L.D. after his transition, and puts him on a Quinjet to save and rescue Daisy and defeat H.I.V.E.
- Melinda - "Gentle" 
- May - Likely to be 梅 in Mandarin Chinese, which means "plum" or "prune".
- Qiu - Likely to be 秋 in Mandarin Chinese, which means "autumn".
- Lian - Likely to be 蓮 in Mandarin Chinese, which means "lotus flower"
- Therefore, her full name in Chinese is 梅秋蓮.
- Her current ID badge serial number is A 078624; the card was issued on 4 September 2013, and will expire on 4 September 2019.
- May has advanced training in weaponry, hand-to-hand combat, close quarters combat, and mixed martial arts.
- She has her pilot's license and is able to fly many different types of aircraft.
- Agent May is shown to be fluent in English, Mandarin and Cantonese.
- She is also known as "The Cavalry".
- May was previously married to Andrew Garner.
- She was Skye's Supervising Officer (SO) (Season 3).
- She loves pineapple as a fruit.
- She hates coffee (Season 2).
- Her birthday is on November 20th.
Jemma Simmons, Leo Fitz: She's the cavalry?
Melinda May: I told you never to call me that.
"Girl in the Flower Dress"
Coulson: Go ahead, say it.
May: I don't do petty.
Coulson: But you called it. I trusted my gut even though you said she was a risk.
May: When someone breaks into my house, I usually don't invite them to stay. But that's me.
Coulson: That's me too. Then that alien staff went through my heart.
May: Sure it didn't go through the brain?
Coulson: You really don't do comforting either, do you?
Coulson: I can't think of a single time when anything alien in human hands ended well.
Skye: Wouldn't mind getting my human hands on Thor. He's so dreamy...
Coulson: Sure, he's handsome, but-
May: No. He's dreamy. [Walks on. The other two stare at her, somewhat surprised.]
Melinda May: You taking a punch for me. I don't need your protection.
Grant Ward: You think I don't know that? I took that punch because you're faster than me. You can do more good on your feet. It was tactical, not personal.
Ward: Really? You think Coulson will take that excuse if he finds out about us?
May: He took it okay when I told him.
Ward: Wait? You told him?
Melinda May: If Coulson thinks there's a chance in a million to save Skye, to save any of us, he'd take it. People like us, we need people like him.
"End Of The Beginning"
Melinda May: You don't believe in the Clairvoyant, but you believe in astrology?
"Turn, Turn, Turn"
Melinda May: I evaluated what was needed, and I gave the assessment to Fury, and he gave you parameters for your unit.
Phil Coulson: What was needed, May?
Melinda May: Someone who could repair your body, a technician who could reprogram your brain, and a specialist to help me put you down if it had to be done. But I didn't do it for Fury. I did it for you, to protect you! I - You mean a lot to me. A lot. To hear you were dead... you may not believe me, but that's the truth. And I have nothing to do with the clairvoyant or this Hydra threat we're up against. Hopefully, this helps prove that.
Phil Coulson: I want to believe you... But you've used that against me this whole time.
Melinda May: I'm furious, but I sure as hell am not going to waste it on a tantrum. I'm gonna mine it, save it, and when we find Ward, I'm going to use every bit of it to take him down.
"Beginning of the End"
Kaminsky: If it isn't the Cavalry.
Melinda May: [Kicks him in the stomach] Don't ever call me that.
Grant. Just like old times.
. May you were never on top. [May knocks Grant in the head with a pole]
"Face My Enemy"
Coulson: This is fun, right? Isn't this fun? Look - Cufflinks!
May: I will pay you $500 right now for a pair of flats.