Billboard Music Awards: What to Expect From the Star-Studded Show

— -- The competition is stiff for the 2015 Billboard Music Awards, airing this weekend on ABC, live from the MGM Grand in Las Vegas.

Taylor Swift is the leading nominee, with 14 entries in 13 categories. Her pal Sam Smith -- who'll be missing the show due to vocal cord surgery -- is nominated for 13 awards in 13 categories. They're both competing for Top Artist, Top Billboard 200 Artist, Top Hot 100 Artist, and Top Digital Songs Artist.

Other top nominees include rapper Iggy Azalea, a finalist with 12 nominations in 11 categories, and Meghan Trainor, with nominations in nine different categories.

"I love the Billboard Awards," gushed Swift in a clip from Countdown to the 2015 Billboard Music Awards. "I always have a great time and I love the fact that the awards are, are based on what the fans have actually decided to invest in and buy."

While Swift isn't performing this year, she'll make a huge impression on the telecast: It'll start with her star-studded video for "Bad Blood," which features the likes of Lena Dunham, Jessica Alba, rapper Kendrick Lamar, Ellen Pompeo, Mariska Hargitay, Hailee Steinfeld, Karlie Kloss, Paramore's Hayley Williams, Ellie Goulding and more, all playing characters with names like "Luna," "Justice," "Knockout," "Destructa X" and "Dilemma." Swift herself is portraying someone named "Catastrophe," and all we know is that there will be fighting involved.

In Countdown to the 2015 Billboard Music Awards, Swift explained the thinking behind the video's concept.

"Let's have them play assassins in a music video," she said. "They are metaphorically killing it. They are also playing killers."

Swift, Azalea and Trainor are all up for the only fan-voted category: the Billboard Chart Achievement Award presented by Samsung, recognizing each woman's huge chart success in the past year.

As far as who is performing on the telecast, the list includes Mariah Carey, Kelly Clarkson, Imagine Dragons, Hozier, Nick Jonas, Tori Kelly, Ed Sheeran, Van Halen, Kanye West, the stars of Empire, Fall Out Boy featuring Wiz Khalifa, Nicki Minaj and David Guetta, Kanye West, Britney Spears and Iggy Azalea, Meghan Trainor featuring John Legend, Pitbull and Chris Brown, Fifth Harmony and Wiz Khalifa, Charlie Puth and Lindsey Stirling. In addition, legendary '80s band Simple Minds will salute the 30th anniversary of their song from the movie The Breakfast Club, "Don't You (Forget About Me)."

The BBMAs will be hosted by rapper/actor Ludacris and model and host Chrissy Teigen. Ludacris told ABC News that of all this year's nominees, he was most impressed by the success of one particular singer.

"I think every year we have someone who is just like a standout person in music and I think Sam Smith takes that cake for this year," he said. "I think he said it best when he won his Grammy. He was like, once he just started being completely honest and pouring his heart out, then everyone started gravitating toward his music and it shined. And I’m extremely happy for him."

The rapper and "Furious 7" star also noted what makes the Billboard Awards different from all the other awards shows out there: They reward the artists and the music that have been most successful on the Billboard charts by measuring actual data: album and digital songs sales, radio airplay, streaming, touring and social interactions.

"It’s based off the charts and it’s not like you can say you don’t know how someone won or certain things like that. So it is based off the people," he explained.

The 2015 Billboard Music Awards air Sunday night, May 17, live on ABC, starting at 8 p.m. ET.

Here are the nominations:

Top Artist

• Ariana Grande
• One Direction
• Katy Perry
• Sam Smith
• Taylor Swift

Top Billboard 200 Album

• Maroon 5, V
• Pentatonix, That's Christmas to Me
• Ed Sheeran, X
• Sam Smith, In the Lonely Hour
• Taylor Swift, 1989

Top Male Artist

• Drake
• Pharrell Williams
• Ed Sheeran
• Sam Smith
• Justin Timberlake

Top Female Artist

• Iggy Azalea
• Ariana Grande
• Katy Perry
• Taylor Swift
• Meghan Trainor

Top Hot 100 Song

• Iggy Azalea feat. Charli XCX, "Fancy"
• John Legend, "All of Me"
• Sam Smith, "Stay with Me"
• Taylor Swift, "Shake It Off"
• Meghan Trainor, "All About that Bass"

Top New Artist

• Iggy Azalea
• 5 Seconds of Summer
• Hozier
• Sam Smith
• Meghan Trainor

Top Duo/Group

• 5 Seconds of Summer
• Florida Georgia Line
• MAGIC!
• Maroon 5
• One Direction

Top Billboard 200 Artist

• One Direction
• Pentatonix
• Ed Sheeran
• Sam Smith
• Taylor Swift

Top Radio Songs

• John Legend
• Maroon 5
• Ed Sheeran
• Sam Smith
• Taylor Swift

Top Touring Artist

• Lady Gaga
• Rolling Stones
• One Direction
• Katy Perry
• Justin Timberlake

Top Social Artist

• Justin Bieber
• Miley Cyrus
• Ariana Grande
• Taylor Swift
• Selena Gomez

Top Streaming Artist

• Ariana Grande
• Nicki Minaj
• Iggy Azalea
• Taylor Swift
• Meghan Trainor

Top R&B Artist

• Beyoncé
• Chris Brown
• John Legend
• Trey Songz
• Pharrell

Top Digital Songs Artist

• Iggy Azalea
• Ed Sheeran
• Sam Smith
• Taylor Swift
• Meghan Trainor

Top Rap Artist

• Iggy Azalea
• J. Cole
• Drake
• Nicki Minaj
• Rae Sremmurd

Top Country Artist

• Jason Aldean
• Luke Bryan
• Florida Georgia Line
• Brantley Gilbert
• Blake Shelton

Top Rock Artist

• Bastille
• Coldplay
• Fall Out Boy
• Hozier
• Lorde

Top Latin Artist

• J Balvin
• Juan Gabriel
• Enrique Iglesias
• Prince Royce
• Romeo Santos

Top Dance/Electronic Artist

• Avicii
• Clean Bandit
• Disclosure
• Calvin Harris
• Lindsey Stirling

Top Soundtrack

• "The Fault in Our Stars"
• "Fifty Shades of Grey"
• "Frozen"
• "Guardians of the Galaxy Awesome Mix Vol. 1"
• "Into the Woods"

Top R&B Album

• Beyoncé, Beyoncé
• Chris Brown, X
• Michael Jackson, Xscape
• John Legend, Love in the Future
• Pharrell Williams, G I R L

Top Rap Album

• J. Cole, 2014 Forest Hills Drive
• Drake, If You’re Reading This It’s Too Late
• Nicki Minaj, The Pinkprint
• Iggy Azalea, The New Classic
• Eminem, The Marshall Mathers LP 2

Top Country Album

• Jason Aldean, Old Boots, New Dirt
• Garth Brooks, Man Against Machine
• Luke Bryan, Crash My Party
• Brantley Gilbert, Just As I Am
• Miranda Lambert, Platinum

Top Rock Album

• AC/DC, Rock or Bust
• The Black Keys, Turn Blue
• Coldplay, Ghost Stories
• Hozier, Hozier
• Lorde, Pure Heroine

Top Latin Album

• Juan Gabriel, Los Dúo
• Enrique Iglesias, Sex and Love
• Romeo Santos, Formula Vol. 2
• Santana, Corazon
• Marc Anthony, 3.0