This is very odd. Originally a French sf movie, an American version was directed by Harvey Weinstein with a script by Isaac Asimov. Voice artists include Glenn Close, Bridget Fonda, Christopher Plummer, Penn & Teller...
The basic plot is straight out of the old pulps, with an apparently Utopian pastoral society based on biological technology under attack by an army of metal men - from the future! There's also a really huge artificial brain, a tribe of cave-dwelling mutants, weird animals and plants of all sorts, and a city with breasts. In fact, there are quite a lot of breasts, because it's French.
The overall mood is oddly upbeat, given that the plot is about botched and thoroughly unethical experiments undermining a splendid but flawed culture. The animation was handled in
Indeed, such an ambitious and - broadly speaking - successful feature film deserves to be considered neglected classic. Loopy? Well, yes, but most sci-fi and fantasy classics are. Explain how Metropolis makes any kind of sense in plot terms, and then we can talk about whether millions of small cyborg birds really could lift a city.