Cool Gardens is a poetry book by the lead singer of the band System of a Down, Serj Tankian.
 It was published by MTV Books and was released on October 1, 2002.
 It is a collection of seven to eight years of Tankian's reflections on life, and features artwork by fellow Angeleno, Sako Shahinian.
 The poetry, like the songs of System of a Down, consists of a reflection of societies and people's wrongs.
 It portrays what people do to themselves and the control others try to hold over them.
System of a Down, sometimes shortened to System and abbreviated as SOAD, is an Armenian-American heavy metal band from Glendale, California, formed in 1994.
 The band currently consists of Serj Tankian (lead vocals, keyboards), Daron Malakian (vocals, guitar), Shavo Odadjian (bass, backing vocals) and John Dolmayan (drums).
Candyland is the tenth studio album by Italian gothic metal band Theatres des Vampires, released through Scarlet Records on 14 October 2016.
 Initially announced on 7 July 2016, it is their first studio album in 5 years since "Moonlight Waltz", and also their first release with guitarist Giorgio Ferrante, who replaced Stephan Benfante early in 2016.
 It is noticeably more guitar-driven than the band's previous releases with Sonya Scarlet on vocals, and its lyrics focus less on the vampiric and occult themes the band is famous for.
 A music video for the track "Morgana Effect" was uploaded to the band's official YouTube channel on 29 September 2016.
Sonya Scarlet (born 2 April 1980) is the singer and lyricist of the Italian extreme gothic metal band Theatres des Vampires.
Bad Acid Trip is an American metal band, currently signed to System of a Down lead singer Serj Tankian's record label, Serjical Strike Records.
 Their 2004 album, "Lynch the Weirdo", was produced by Daron Malakian, another System of a Down member.
 In 2006 they performed on the second stage at the Ozzfest summer tour.
 The band has three full-length releases ("For the Weird by the Weird", "Lynch the Weirdo", and "Humanly Possible") and multiple EPs.
"Mein" (German for either "mine" or "my") is the second single from the American alternative metal band Deftones' fifth album, "Saturday Night Wrist", and their 11th single overall.
 The song featured Serj Tankian of System of a Down on vocals.
 The single was released on March 13, 2007.
The Addiction Tour 2006 is the first live DVD by the Italian gothic metal band Theatres des Vampires.
 It features ten songs recorded during the tour in 2006 and also features an interview with Sonya Scarlet, as well as two music videos the band had recorded for the songs "Lilith Mater Inferorum" and "Angel of Lust".
 The live songs were also released as a live album in the band's next release, Desire of Damnation.
Screamers is a 2006 documentary film directed by Carla Garapedian, conceived by Peter McAlevey and Garapedian and produced by McAlevey.
 The film explores why genocides have occurred in modern day history and features talks from Serj Tankian, lead vocalist of the American alternative metal band System of a Down, whose grandfather is an Armenian Genocide survivor, as well as from human-rights activist, journalist, and professor, Samantha Power, as well as various other people involved with genocides in Rwanda and Darfur.
 "Screamers" also examines genocide denial in current-day Turkey, and the neutral trend that the United States generally holds towards genocide.
Elect the Dead is the debut album by rock musician Serj Tankian, lead singer and founding member of Armenian-American metal quartet System of a Down.
 It was released on October 22, 2007.
 Alongside Tankian appears Armenian-American coloratura Ani Maldjian, drummers John Dolmayan from System of a Down and B. Brain Mantia of Primus and Guns N' Roses, Dan Monti on guitars, as well as a string section featuring Antonio Pontarelli.
Serj Tankian (Western Armenian: Սերժ Թանկեան , ] ; born August 21, 1967) is a Lebanese-born Armenian-American singer-songwriter, composer, multi-instrumentalist, record producer, poet, and political activist with Armenian descent.
 He is best known as the lead vocalist, songwriter, keyboardist, and occasional live rhythm guitarist of the metal band System of a Down, formed in 1994.

Question: Have Sonya Scarlet and Serj Tankian both been singers in a metal band?
Answer: yes