Bryar joined My Chemical Romance shortly after the release of the band's second studio album Three Cheers for Sweet Revenge in 2004, replacing former drummer Matt Pelissier.

[10][11] A month later, the band missed two tour dates after Bryar was hospitalized with a staph infection also caused during the filming of the music video.

On July 31 and August 1, they played two "secret" shows at the Roxy Theatre in Los Angeles, performing unreleased material from their upcoming album, including a song titled "Death Before Disco".

Iero explained that the incident was a turning point in Bryar's relationship with the band, stating that "he just couldn't keep it together anymore" and that his "sadness, anger and distrust were too much to handle and took over all aspects.

[30] After his departure from My Chemical Romance, Bryar continued being involved in the music business as a behind-the-scenes figure in tours for several bands.

[33][34] On July 20, 2016, My Chemical Romance posted on their official Twitter and Facebook pages a video with the piano intro from "Welcome to the Black Parade", ending with a cryptic date, "9/23/16".

[37] This led to numerous rumors and reports on the band's possible reunion until it was revealed to be a reissue of The Black Parade with unreleased demos.

In his first interview since departing from the band, Bryar recalled multiple memories of recording and touring The Black Parade.

[31] In June 2021, Bryar announced that he had officially retired from drumming, citing his ongoing wrist issues, age, weight, and his desire to pursue "something new.

"[44] During his time with My Chemical Romance, Bryar was known for using kits made by C&C, a custom drum company based in Gladstone, Missouri, paired with Sabian "Paragon" cymbals and Remo heads.

[citation needed] Following his departure from My Chemical Romance, Bryar was active in dog rescue charities and sanctuaries.

[31] In June 2021, Bryar auctioned his Helena-themed drum kit on eBay and dedicated the money to the Williamson County Animal Control and Adoption Center located in Franklin, Tennessee.