"[12] This album marked a definitive change in musical scope for Nightwish from their folk-laden roots in Angels Fall First, showcasing a more bombastic, power metal-oriented[13] sound with faster tempos, harmonic guitar/keyboard leads, and plenty of double-bass-heavy drumwork.

[14] Oceanborn's sound hearkens a more dramatic approach in the overall musical scope, mostly relegated to the symphonic keyboard work and lead singer Tarja Turunen's vocals.

According to Mape Ollila, who penned the band's biography: Along with Therion's Theli, the album came to be known as one of the cornerstones of the emerging genre of symphonic metal.

[15] Most of the lyrics are fantasy-themed, with tracks like "Swanheart" and "Walking in the Air", a cover from the animated TV special The Snowman, as typical examples; however, the song "Gethsemane", has a more religious feel to it.

Oceanborn is among their darkest albums, making use of the harsh vocals of Tapio Wilska in the songs "The Pharaoh Sails to Orion" and "Devil & the Deep Dark Ocean".