When you watch an anime, you want the right mood from the get-go. In order to accomplish this, many anime have opening songs, or OPs, that play before the episodes start. Like everything, these can be done right, or wrong. Luckily, these six songs right here not only set the mood for their respective series, but also sound really good.

1. "Again" by Yui from "Fullmetal Alchemist: Brotherhood"

Even though "Fullmetal Alchemist: Brotherhood" has its lighthearted moments, there's certainly an equal amount of heavy moments. This sporadic rock number from Yui serves as the first opening for the series. It starts out soft and mid-paced, representing the underlying tension in the show's themes. This is followed by a fast-paced guitar riff with more intense vocals from the singer, which mirrors the show's more emotionally heavy moments. "FMA:B" has several great opening themes, but this is definitely the best one.

2. "Perfect-area Complete!" by Natsuko Aso from "Baka and Test: Summon the Beasts"

First, I have a disclaimer. Please do not watch "Baka and Test." If you already have, I am dreadfully sorry that you had to endure numerous several sexual themes. The show's humor was great for a while, but the fanservice became overpowering, so I dropped the show after 3 episodes. That being said, the show had a great opening. With a fast-paced dance-pop beat and lyrics about going to school, this definitely matched the show's fast-paced dialogue and humor in the school setting.

3. "Alones" by Aqua Timez from "Bleach"

"Bleach" had several opening themes, and I thought most of them weren't that great. This, however, is an exception. This particular song plays during the Hueco Mundo arcs, in which Ichigo Kurosaki and his friends attempt to rescue one of his kidnapped friends, Orihime Inoue, from the lair of series antagonist, Sosuke Aizen. This pop punk tune is slightly melancholy, but has hopeful undertones. This is a fitting mood for that particular spot in the story as Ichigo braves the dangers of Hueco Mundo to save Orihime.

4. "World's End" by FLOW from "Code Geass: Lelouch of the Rebellion R2"

Again, this show is hard to recommend because of the heavy fanservice. However, the show had one of the best stories ever and several great openings as well. This song is the second opening for the second season. The song has a slightly anthem like tone as series anti-hero Lelouch vi Britannia slowly loses his sanity as he attempts conquering the Holy Britannian Empire.

5. "To the Beginning" by Kalafina from "Fate/Zero 2"

"Fate/Zero" is a fantastic fantasy anime. Though I wasn't a huge fan of where the story went in season 2, I liked season 2's opening and ending the most. Kalafina, a pop rock group formed by famed anime composer Yuki Kajiura, does a fantastic job capturing the mood for the second season. While the first season focused on character development and unification against a common enemy, the second season focused on the characters' final moments as they continue to fight each other for the Holy Grail, while slowly learning its secret. The song has a somber, but optimistic tone which mirrors the hope many of the characters have for the future.

6. "My Soul, Your Beats!" by Lia from "Angel Beats!"

Finally, we have light piano number written for a supernatural comedy-drama. This song proves that opening songs don't need guitars to be awesome. Played with a piano over a light electronic beat, this song has a happy, but cautious tone. This matches the characters' struggle to find peace in the afterlife, which involves lots of comedy and emotional moments.

I hope you all enjoy these!