With other complementary artifact mana sources like Thran Dynamo and Grim Monolith, decks could count on being able to get the kind of mana you'd need to justify packing the cards that would let you use the mana from Metalworker to deliver the knockout blow, and their presence lets you turn that Metalworker mana into permanent giant amounts of mana rather than just a one shot deal
1 Blessed Breath
While these interactions arent too unfathomably complex, they dont present themselves immediately when looking at a Polluted Delta
Press the advanced filters button, to the right of the card types option bar, which shows three lines
You do get two cards, so there is some incentive here to make this on or off draw work more often than not
Funnily enough, I had a quick look at the Cloudpost deck that made the Top 8 of the very first Modern Pro Tour in Philadelphia back in 2011, and the deck contained four cards that are now banned Cloudpost, Eye of Ugin, Green Suns Zenith and Punishing Fire