Lewis is known for her expansive four octave vocal range, power, technical control and, in particular, her frequent use of the falsetto register.
Aside from her musical career, Lewis is a philanthropist and an animal welfare campaigner for World Animal Protection and is a supporter of other animal rights charities and organisations; she is also a vegetarian.
In February 2007, Lewis signed a five-album contract in the United States with Clive Davis’ record label, J Records.
Lewis's success continued with the release of her debut album, Spirit, in 2007; it went 10× platinum in the United Kingdom and became the fourth best selling album of the 2000s.
Under the guidance of Cowell and Davis, Lewis released her second UK number-one album Echo and recorded the theme song for the film Avatar in 2009, while embarking on her first UK arena tour, The Labyrinth, in 2010.
In the United Kingdom, it broke a world record after being digitally downloaded more than 50,000 times in less than 30 minutes.
In 2014, Lewis made her film debut in the supporting role of Elena in the romantic comedy musical, Walking on Sunshine.
In 2016, Lewis made her Broadway debut as Grizabella in the revival of Andrew Lloyd Webber's musical Cats; she played the role from that July to October.
The album has sold over 9 million copies worldwide and has a 9× platinum certification in the UK where it is the fourth best-selling album of the 2000s decade.
Lewis's second single, "Bleeding Love", produced by Ryan Tedder and written by Tedder and Jesse Mc Cartney, was released in October 2007 in the UK, where it sold 218,805 copies in its first week, giving it the biggest first-week sales of 2007 to date.