A new, never before seen species of Pokemon has been discovered and Meltan, as it's called, is made of steel, duh, and belongs to the Hex Nut Pokemon family. Professor Willow will apparently have some special research later this year.
The little guys are quite metal friendly, or unfriendly - depending on whether you don't mind missing cutlery, which they really enjoy incorporating into their little bodies, Terminator style. Except they're much cuter, as you can see.
Niantic wrote that Pokemon Go's professor duo Willow and Oak have made some progress investigating these mysterious Pokemon, but they'll be needing help. As you carry out research, you'll be learning more about Meltans, as long as you stay away from wrenches. Just kidding, they'd probably eat them up.
Niantic also announced that Pokemon Go will be getting a bunch of changes soon, based on trainer feedback. The changes are split into two sections, with the first one having to with Pokemon migration and behaviour.
Adjustments are being made on the weather, which will now have a reduced effect at appearance rates of Pokemon. Apparently, as you explore an area, you'll be seeing a greater variety and spawn rates of Pokemon over time.
Additionally, parks and nature reserves will feature more varied Pokemon species, which is as good a reason as any to visit your local landmarks. Heck, Pokemon GO is probably the only reason many will.
The second part of Pokemon GO changes is related to their effectiveness in battle. Niantic wrote that CP and HP values will be adjusted, with the latter aiming to bridge the gap between low and high HP Pokemon. Defense and stamina values will be tweaked too, "allowing highly defensive Pokémon to be valuable in battle by outlasting opponents rather than simply running out the clock."
If you're interested in learning more about Meltans, you can do so in Niantic's other video here, where Willow and Oak explain how they unlocked the little devils. As for Pokemon GO's balance changes, you can find Niantic's full list here.