Lee has stated in several interviews that she likes to experiment with different musical elements and doesn't like "doing the same thing over and over again”. She has experimented with electronic music, most prominently in the first sessions of the pre-production phase of the bands’ third album. She has also expressed interest in folk music.
Lee has been classically trained in piano for 9 years and uses simple chords with left-hand backing in songs. She often includes the piano as a main or background instrument into the bands’ music, most prominently in the album "The Open Door". Several music critics consider the piano accompaniment as a characteristic feature of Evanescence’s music. Lee often plays the piano during live performances in selected songs, and has been known to cover songs on the piano as well, such the Korn song “Thoughtless”. She can play the acoustic guitar and has been training in harp, lightly utilizing this instrument in the bands’ third record, most prominently in the song “Secret Door”.
American recording artist Kelly Clarkson described Lee's concert performances as "intense" and thinks that she's "a beautiful vocalist, and has great taste in melodies and music". Clarkson also revealed through her Twitter that she would like to sing a duet with Lee.
Lee's vocal range spans 3.6 octaves from a low A2 (2003 Fallen Vocal warm up) to an E6 in full head voice (MTV Video Diary). Her highest recorded note in full head voice is a C#6 in the song “Weight of the World" and her lowest recorded note is a C3 in the cover of U2's song “With or Without You". Lee's highest mixed note in studio recording is a G#5 in the collaboration with American rock band Halestorm's song “Break In”. Overall, her highest mixed note is a Bb5 in a cover of Michael Jackson's song “Dirty Diana". Lee has also been known for her scream in the song “Tourniquet” also, in which is in the note of a D5. In an MTV special, Lee managed to hit an E6 live during a vocal warm-up in full head voice, also showing that she is capable of reaching up to Bb7 through exclamation. She is popularly classified as a full-lyric mezzo-soprano, though this has not been confirmed by Lee herself.
Lee is not professionally trained in singing and applies what she learned from her years as a choir member in high school. Her lower to mid-range belts are often supported, if not resonant, and she can sustain notes in the 5th octave in all vowels. She also uses several vocal dynamics in her singing, most notably crescendos.
Critics often consider Lee’s vocals to be one of the highlights of the bands’ music, describing it as “ethereal”, “dramatic” and “haunting”, while praising its “powerful”, “crystalline” and "operatic" qualities.
A very notable theme in Lee's lyrics is relationship struggles. She often identifies various events in life with a story between herself and a lover, evident in the song “What You Want” which is actually inspired by her love for her band and fans. She also writes about her actual relationship struggles, examples include “Call Me When You’re Sober”, referring to her ex-boyfriend Shaun Morgan. Additionally, she often incorporates dark and mysterious themes into the bands’ music, and has mentioned that she is particularly fascinated with the idea of death and beyond. She also resorts to imaginative and picturesque themes as seen in songs such as “Imaginary” and “Lithium”. The songs “Hello” and “Like You” were written in honor of Lee’s deceased sister.
Furthermore, Lee’s songs are generally inspired by her life struggles and personal experiences. “Bring Me to Life” was written after meeting a psychiatrist who understood her hidden feelings, while “Snow White Queen” was written after a turbulent experience with a stalker. She described her writing process in the song “All That I’m Living For”, explaining that she mostly writes at night time.
After Moody's departure from the band, Lee dismissed the public assumption that Evanescence's music would be softer and that "all the sappy stuff comes from [her]", explaining that Moody was "more about the pop influence and being commercial" while she wanted to do "the more artistic, weird thing".
Lee wrote most of the bands’ self-titled album with the fans in mind, describing her relationship with them through different lyrical themes. She also explored more into global issues such as sex trafficking and the Tohoku earthquake and tsunami for this album in the songs “My Heart is Broken” and “Never Go Back”, respectively.
Lee was honored by the National Music Publisher's Association with their 2008 Songwriter Icon Award, which recognizes outstanding songwriters for personal achievement. Lee received the award during the annual NMPA meeting in New York City and performed a song to the attendance as well.
Lee has an eclectic clothing style mostly inspired by Victorian, Gothic and Japanese fashion. She is known to design many of her outfits, such as the outfits she wore for the video of “Going Under” and the dress she wore to the Noble Peace Prize concert in 2011. She occasionally makes her clothes herself. In an interview with VEVO stylized, Lee showcased and explained her fashion style, commenting that she’d rather make her own clothes because it’s hard to find what she exactly wants elsewhere. Lee stated that her daily style is very different from when she performs; describing it as "funky, spooky, cute" in an interview. She explained that her on-stage wardrobe was meant to preserve the atmosphere of the songs and complete the image. In another interview, she stated that when the band first started performing, she used to heavily wear corsets in fear of diluting the bands’ image, but has gradually become more comfortable with her own style. Her current on-stage style is often characterized by boots, a simple black tank top, a skirt and various ornaments and accessories.
Furthermore, Lee dyes her hair jet black. During the Fallen era, she used to use blue contact lenses and had a distinct piercing on her left eyebrow. She has not used them since.
Many fans admire Lee for not using sex appeal in her music. Lee frequently criticized women who are involved in show-business for abusing their positions as idols by sexualizing their image. The song “Everybody’s Fool” was written by Lee to mock such celebrities after seeing how her sister was infatuated by this trend. The video to this song emphasizes how celebrities peddle lies through projecting an image opposite to who they are.
In 2005, Lee came in 4th in Kerrang!'s 50 Sexiest People in Rock list. She was listed in Blender as one of the hottest women in rock in 2006, alongside other singers such as Joan Jett and Liz Phair. Revolver Magazine named Lee the #1 Hottest Chick in Hard Rock for their 2011 annual issue and she appeared on the front cover. When asked about this in an interview, Lee responded "You have to look at all of that as just press. I'm not the hottest chick in whatever. I'm a normal girl and it takes a lot of makeup and retouching to make that cover look good". She also came in at #9 in KROQ's 2011 list of "The Twenty Sexiest Singers of Female-Fronted Rock Bands".
Lee is married to therapist and long time friend Josh Hartzler. They were engaged on January 8th, 2007, with Lee making the first official announcement on January 9th. They were married on May 6th, 2007 and through a post to the bands' fan club message boards, she announced that she was "officially Mrs. Amy Hartzler". Hartzler was the inspiration behind the songs "Bring Me to Life" and "Good Enough".