Songfacts®:

• Sia wrote and performed this orchestrated ballad for the Fifty Shades Darker soundtrack. The Australian previously contributed "Salted Wound" to the first Fifty Shades movie.
• Sia wrote the song with her frequent collaborator English singer-songwriter Chris Braide, who has also worked with artists like Britney Spears ("Perfume") and Christina Aguilera ("Blank Page").
• Sia sings during the song about the strength that she gets from being in a relationship.
  
  And if you let go I'll float towards the sun
  I'm stronger 'cause you fill me up
  But when the fear comes and I drift towards the ground
  I am lucky that you're around
  
  Sia is comparing the uplifting effect of love to the way helium lifts up a balloon.
• Helium is a colorless, odorless, gaseous element. Here are some fun helium facts from The Encyclopedia of Trivia.
  
  French astronomer Pierre Jules César Janssen discovered helium in 1868, while analyzing the chromosphere of the sun during a total solar eclipse in Guntur, India.
  
  Because helium was found in the Sun before it was found on Earth, its name comes from the Greek word for Sun, helios.
  
  Although helium is the second most abundant element in the universe, most of it in the Earth's atmosphere bleeds off into space.
  
  Helium is one of lightest and least dense of all the elements. Its low density is what causes balloons filled with the gas to float, buoyed up by the denser surrounding air.
  
  When Helium is cooled to almost absolute zero (-460°F or -273°C), the lowest temperature possible, it becomes a superfluid with unusual properties: it flows against gravity and will start running up and over the lip of a glass container.
  
  Today, the US alone produces 75 percent of the world's helium. Nearly half of that total, or roughly 30 percent of the world's helium supply, comes from the U.S. Federal Helium Reserve. That reserve is held in a huge natural underground reservoir near Amarillo, Texas called the Bush Dome.