According to Duff, the album incorporates elements of pop and rock music, and it represents changes that are specific to her life and that everyone experiences.

Later the album was certified quadraple platinum by the Recording Industry Association of America (RIAA) for shipments of over four million copies in the United States.

For Hollywood Records, Metamorphosis was the label's first high-seller in several years and led to the company's further successful cultivation of new artists and brands using the Disney Channel.

Her songs "I Can't Wait", "Why Not" and "What Dreams Are Made Of" were hits on Radio Disney, but Recke and executives at Buena Vista Music Group envisioned Metamorphosis as a vehicle by which Duff could reach a more mature audience.

"[10] As Duff was really into Destiny's Child at the time, initial work on the album carried a more "urban style" than the finished project.

[2] Kara DioGuardi, who had long outgrown Disney, thus making her unaware of who Duff was, was told by an acquaintance of hers who worked at EMI that she should meet up with Recke.

[2] Pettus deemed his involved in the project as being "completely accidental"; he had just moved from New Jersey to Los Angeles and was introduced to Midnight through their mutual friend Marc Swersky.

[2] The Matrix, a record production team consisting of Lauren Christy, Graham Edwards and Scott Spock had "just come off the back of a very successful little run" with three number one hits with Avril Lavigne when Disney approached them and asked if they would be interested in writing for Duff.

[2] At the time, she had just finished work on Marc Anthony's sixth studio album, Mended (2002), and was "really, really uninspired writing to tracks".

She said that there are many "different sounds" on the album, such as rock and electronic, and "a whole range" of tempos, including "deep, slow" tracks and "high-energy" songs to provide her with a "boost".

[9] Rolling Stone magazine described the album as "a slick collection of pop songs, master-crafted to appeal to huge numbers of young people".

[9] The final song on the album, "Why Not," was previously released on the soundtrack for The Lizzie McGuire Movie, a film in which Duff starred.

During the period in which Metamorphosis was released, Duff was participating in many projects in film, brand licensing, music and television; USA Today wrote in July 2003 that she was emerging as "The Next Big Thing" and "a marketing powerhouse" with nine to twelve year-olds, and Billboard magazine said that she "is looking to become more than just the nation's next teen pop princess.

Entertainment lawyer Larry Golring called it "a great cross-promotion" for VideoNow and Duff's music career, which he said were "two new brands that are going to be huge this time next year, and they hopefully will have helped each other get there".

[21] The Associated Press quoted Bob Cavallo, the chairman of Buena Vista Music Group, as saying that "At this point, she's obviously already a franchise".

[16] Marketing people such as Laura Groppe, president of Girls Intelligence Agency, said that the timing of the release of Metamorphosis and other Duff-related products was right because there had been a lack of teen idols since Britney Spears, and that Duff "[is] not too pretty.

[20] Amy Doyle, at MTV's vice president of music programming, said Duff was "definitely one of the hot people to watch ... She's become the fabric of pop culture with teens right now.

[20] Others, such as Robert Thorne, the CEO of the Olsen twins' Dualstar Entertainment, said that Duff should have stayed with The Walt Disney Company — from which she separated after contract negotiations broke down — to build the Lizzie McGuire franchise and use it to help develop her career into adulthood.

[15] A DVD containing music videos, performance and behind-the-scenes footage and bonus features, Hilary Duff: All Access Pass, was released in November.

[29] In the same period she embarked on a U.S. summer tour, during which she performed a one-hour set that included Metamorphosis tracks, covers of The Go-Go's' "Our Lips Are Sealed" and The Who's "My Generation", and previously unheard material from Hilary Duff.

Haylie Duff was the opening act on the tour, which ran for thirty-six dates and sold well in major arenas; Pollstar editor-in-chief said that there was "a real positive buzz about ticket sales for Hilary's show".

[33][34] The song, written by Lauren Christy, Scott Spock, Graham Edwards and Charlie Midnight, was produced by production team The Matrix, who were notable at the time for their work with Avril Lavigne.

It reached a peak of number seventeen in Australia and eighteen in the UK, while charting inside top twenty in Canada, Netherlands, Ireland and New Zealand.

[20] Stephen Thomas Erlewine of AllMusic wrote the album, "is what teen pop should sound like in 2003... a very good modern bubblegum album"; he said that it was influenced by Avril Lavigne but that Duff "has a sweeter, more appealing voice than Avril, and the rest of the record follows her cheerful charisma, resulting in a charmingly effervescent listen".

[53] Blender magazine called it "a masterfully executed tour through contempo mall-pop, '80s new-wave bubblegum and girl-power affirmations".

[56] USA Today named it the tenth worst pop album of 2003, writing "Note to all young, modestly talented singers: Stay in school and you won't wind up on worst-of lists before you're old enough to vote.

"[57] Metamorphosis was nominated at the Juno Awards of 2004 for International Album of the Year, but lost to 50 Cent's Get Rich or Die Tryin'.

In late November/early December, after Duff had appeared at the Macy's Thanksgiving Day Parade and sneak previews of the film Cheaper by the Dozen were held in select cities, Metamorphosis returned to the top five on the albums chart with a 132% sales increase over the previous week with 224,000 copies.

The San Fernando Valley Business Journal wrote that the album was "giving Hollywood Records a needed shot in the arm" after a decline in CD sales during the previous two years had forced the label to reduce costs and alter its operation.

Bob Cavallo attributed the album's success to Duff's amassing of fans of the singers and former Disney "Mouseketeers" Britney Spears and Christina Aguilera.