Metal EVE is a unique character, you can't really have another Metal EVE. She's a one of a kind character. What do I mean by this? Well, Metal EVE is a character whos new to an existing set of people. Sure, Ai fits this description when she's introduced, so does Lucky, but Metal EVE has something that non of those other characters have; learning HOW to be an animal, learning HOW to live in these woods. Ai and Lucky already knew things like emotions, and how life is to be lived, but Metal EVE, she was a robot, she didn't know, but she learns, and develops.
In Machine Mayhem, from page 127 to page 131, the chapter "Upgrades" happens. Why is this relavant? Well, it is the chapter when Skunky expresses a desire for tea, and looks at Metal EVE. Metal EVE says "What? I'm not making you one.", and Skunky asks "Then what did I design you for?" Metal EVE responds with "I wish I knew! You created me to be super efficient, and gave me no purpose! Now my memory nodules have corroded with the boredom." Skunky responds with "Purpose? Well if its purpose you want..." 
"I'll plug you into the mains!" Skunky does that and gives Metal EVE full access to the control panel of the central network of his laboratory, and so Metal EVE makes the tea, but says that she can't just waste time making him tea. Skunky says that she's gone a bit rouge and tries to unplug her, but Metal EVE wraps him in wires to prevent him and become the Machine.
Now, what does she gain from this? What is the purpose she finds in this? Well, i'll tell you! From pages 147 to 151, in chapter "Down Below" it is revealed that Metal EVE's goal is to take over the woods, with help from Metal STEVE. She asks why Skunky left in such a hurry, and Skunky says that he went to get cheese. Metal EVE asks if he got some and Skunky says that they only had red leicester and that he hates red liecester. Metal EVE says that she has an envoy above ground because she is stuck down in Skunky's lab. Earlier in the book, Skunky tried to trap Metal STEVE in a box and switch him off, so Metal EVE, knowing that these two are a threat to her plans, tries to get Metal STEVE to switch them off. See how far she goes to stop her plans being thwarted?
Okay, so now you know what she is trying to do, but what is the WHY? Well, in pages 229 to 231, while she is starting the Rise of the Machines, sending out robots and turning everything into a robot, Pig goes on his way to send her a present. When Pig gets to her, she brings him to her central core, because his innocence intriuges her. Down there, she explains how she can observe every inch of the woods, and how she saw it all turn to dust, over and over again, then she says this:
"Life is fragile, and must be preserved. I shall save this world. by incasing it inside metal,"
Finally, now we know what she wants, what her motive is for taking over the woods. Wait wait wait, before we continue, let us go back to before Metal EVE became The Machine and started the Rise of the Machines, from page 81 to page 84, in the chapter "So Beautiful", Weenie finds Metal EVE in the woods. She explains that she has left the laboratory on a field excursion to better understand the outside world (Excursion means a short trip or journey) to aid her in her calculations. Metal EVE is confused and asks Weenie what beautiful is, because she overheard her talking about all the beautiful things in the woods. 
Weenie explains that beauty is when something is so nice to look at, it makes you feel all happy and floofy inside your tummy! She talks about the beesnest, full of happy, smiling bees and tells Metal EVE that it's beautiful. Before Metal EVE can respond, or even think, Monkey comes in some machine that splashes jam everywhere, so Weenie then points to the ladybugs walking around and says that they're beautiful. Metal EVE analyzes them for a probability of beauty and finds nothing, for she is looking at the world with a calculating view, saying that they are insects, acting out simplistic routines to aid their survival, and that there is minimal beauty. And then Monkey gets stung by bees because the bees are mad he splashed jam on their beehive, and Metal EVE says that was beautiful and Weenie agrees.
You see how concepts that the other animals already know, like beauty, are new to her, and she learns them in her experience, and she has a very wrong idea of what life's meaning and so goes far to protect it, by encasing it in metal in the later chapters?! Metal EVE is a good character because of how she develops and how far she is willing to go to achieve her goals. Now, lets go forward again, and continue when Pig is giving Metal EVE the present.
So Pig tells EVE that he got socks for Christmas, and tells EVE that pigs don't wear socks. EVE says that this is indeed, illogical, so Pig says that he will put them on his hands and pretend they're snakes (Yes, hands, even though he has hooves.) and does so, making the moo noise as he pretends they are snakes. EVE points out that according to her database, cows do not moo, so Pig does the quack sound instead. EVE laughs, and says "Laughter. I... laughed. I've never felt an emotion before", so this is the first time she has ever felt an emoition. Another concept the other animals already understood and knew since the begining and which she knew of before, but now feels and understands this concept. Now this is the point, the point where she learn's life's true meaning.
At first she asks where it went, and says that she wants it back, and then she realizes that life is to be experienced, not to be preserved. I will quote Metal EVE from this scene here:
"Hee hee! Laughter. I... laughed. I've never felt an emotion before. Where's it gone? I want it back. I... Oh my gigabytes, i've been so wrong! The world was never meant to be preserved. It is to be experienced. The joy of being alive comes from just how fleeting it is! How finite. How temporary. How small the moments. How wonderful. The Rise of the Machines is cancelled. For now I know life's true meaning. And it is precious." -Metal EVE, Machine Mayhem. 
Metal EVE learns what life's meaning is and what her purpose is, and this is the point on where she becomes good, and not evil. Well technically she became not evil when Skunky plugged the USB into her and took away the file which is her thirst to take over the world, and it is implied that she would have taken the meaning of life to the extreme and try to take over the woods again, just in a different way had Skunky not taken this file out, but still, she develops. I want to point out another Metal EVE scene that I really like that shows more of her development as a character. In the next book, Multiverse Mix-up, she sits, watching the Monkey suck up all the snow with the thing that lets him suck up all the snow while the other good woodland animals try to stop him, watching the fight ensue, purposeless, motiveless, ever since Skunky had removed her evil. Bunny hands EVE a branch and says to help them defeat Monkey, and that it might cheer her up.
So EVE helps them by hitting Monkey with a branch and says "This is fun! WHY is this fun?" And Bunny, Ai and Weenie respond with "Because Monkey is mean, and cruel, and selfish" and Bunny ends that with "And thwarting him keeps the rest of us safe." EVE joins Bunny's team later in the book, officially becoming a GOOD GUY! Well, she became a good guy when Skunky removed her evil and she learned the true meaning of life, but its official from this point on. Do you see how she finds her purpose in life and her place among these woods? Now, yours truly must now continue working on my thing, because I believe you know know in detail why Metal EVE is my favourite. If you do, then I believe I have done my job, goodbye!
In case you are curious, this article has 1464 words and 7787 characters, not including this line where I give you this information.