I'm looking for white or green cards that turn an artifact into a creature indefinitely while retaining their abilities (similar to March of the Machines). Is there a card like that?
It has equal converted mana cost. The most signficant difference to March is that the animated artifacts lose their abilities.
I found that card through this Gatherer search, so you might find something else to your liking, or you could refine the search to include other cards. For example, Karn, Silver Golem is an artifact creature that also animates artifacts, except one by one and only until end of turn.