Told you I'd do a Missed Music. Anyway, this is going to be done a little differently. First I will tell you the name of the band, then their genre, then what album(s) I recommend you try first if you want to get into them, then a brief description and finally I'll link you to a pair of songs on youtube (just songs, not music videos) by them that I think would help you figure out whether you'll like them. I dunno if I'm connected enough to the obscure side of music to get enough to fill a second post, but if you like this, I'll give it another shot.
Tegan and Sara
Genre: Indie Rock?
Recommended first album(s): Either The Con or Sainthood
I first discovered Tegan and Sara when Rock Band 3 came out and included their song The Con on it. This led me to investigate them and they rocketed faster to my top 5 favorites of all time faster than any band I had discovered like that, which is really the best sort of compliment I can give.
As for their music, indie rock is the best term I can come up with, even though it doesn't really mean anything (it's used as a blanket term for things that are had to classify), but really these ladies defy genre. Rock, folk, new wave, who knows? Whatever, they're a preciously unique gem in the dull gray waters of the modern music industry. I must say that most people who know me well are unsurprised to know I'm fond of them, as they're heavily lyric based and poetic, without resorting to word salads and occasionally anthemic, things I'm very fond of.
Quick side note before I hit the links for the songs: Those fans of Jonathan Coulton in the audience may recognize Sara as the replacement voice for GlaDOS for the version of Still Alive from Artificial Heart. Alright, moving on.
Genre: Celtic Metal
Recommended first album(s): Everything Remains (As It Never Was)
I've long enjoyed alternate forms of metal, be it Prog Metal (Dream Theater), Viking Metal (Tyr) or Pirate Metal (Alestorm and YES that is as awesome as it sounds). But being Irish, I'm often very fond of Celtic forms of music, such as Flogging Molly, The Pogues or Thin Lizzy. And, really, how can you go wrong with Metal sung in Gaelic?
The Celtic influence moves beyond the mere aesthetics of the thing, such as the Uilleann Pipes (know your bagpipes) in the music, or the Gaelic lyrics, and right to the core. For example, I'm 99 percent certain that Quoth the Raven is about the Morrigan (I've read the Ulster Cycle, sue me). If you like Irish things and metal, this band is definitely for you.
Genre: Punk Rock
Recommended first album(s): Public Display of Infection
Again, this band was first introduced to me via Rock Band, back when they were known as Vagiant. They went through a couple rebrandings and came out the other side Tijuana Sweetheart.
I'll warn you up front, this band isn't for the easily shocked (although who among punk fans is easily shocked?) Most of their songs are either about mayhem or sex (or both) and some of it can be...kind of explicit. They have a song that is literally about giving Jesus a blowjob (and people wonder why I like them?) But if you like Punk, they're well made Punk Rock with good lyrics and some great guitar sections. Currently they're a deeply obscure band, so it'd be nice if they had some success. So if you're into punk, give them a look.
Genre: Fucked if I know
Recommended first album(s): Opheliac
That genre description isn't kidding either, Emilie is even harder to classify than Tegan & Sara. Put quickly, her music is like if Lady Gaga moved to England, developed real talent, began using classical instruments, started writing proper lyrics and decided to focus that craziness that drives those ridiculous costumes into her songs (not that Miss Autumn is any stranger to costumes). This is what drives me crazy about Lady Gaga, her insane public persona is so heavily at odds with the generic techno-pop of her music. But that's not what this is about.
At the core of Emilie Autumn is a mix of Neoclassical (yes that's a real thing), industrial and rock, but like Tegan & Sara, she defies genre. I will say that those of you who are into steampunk will find a lot to like in her aesthetics and those of you who like good (if often depressing) music and lyrics, will find a lot to like in her songs. So do give her a look.