Saeviomagy
Adventurer
For starters, I think that metamagic feels like a mechanic that was just chucked on sorcerors because they couldn't think of anything else to do with them. Heck, they don't even get metamagic until 3rd level. I'd much prefer to see sorcerors get something truly flavoursome, and I think that having them take a subclass at 1st level and giving them bonus spells like the favoured soul has helps with that.I think Metamagic is basically the main reason for playing a Sorcerer over a Wizard (a second reason being perhaps being attracted to one of its subclasses) and it's not even a very strong selling point. Metamagic feats would kill the Sorcerer class for the rest of the edition, unless they were meant strictly for the Sorcerer i.e. they would require to already have a source of spell points. This would not be a bad idea in fact, considering that Sorcerers get quite few metamagic effects overall.
However
I would also say that if you give access to one metamagic ability, along with "convert spell slots to sorcery points", then you're still going to be behind the sorceror in terms of how much you make use of the feature. Plus it costs you a feat to get.