After years of popularity in the alternative rock scene, Dave Grohl wanted to express the passion for heavy metal he bore since his youth.

He mentioned the catalyst of the experience being during the first leg of the tour in support of the Foo Fighters album There Is Nothing Left to Lose, with the mellower songs making him think about the heavier bands he used to listen to.

[3] He came up with "my wish list of all of my favorite singers from this era which is '82 to '89 underground metal, and all the bands I listened to at the time: Eric Wagner from Trouble, Snake from Voivod, Cronos [from Venom], Lemmy and Wino," and started contacting the musicians,[4] some of whom were reached by Grohl's friend Matt Sweeney given the Foo Fighters had restarted their tour.

[1] Grohl feared his fame built out of being "a stupid, middle-of-the-road, alternative-rock idiot" could drive the metal singers away, but many agreed immediately.

Each track on the album features a different lead singer including Lemmy, Max Cavalera, King Diamond and Tom Warrior.

after Grohl approached him regarding writing lyrics, his spouse Tanya Haden suggested "it should be about a fucked up relationship," so Black made it about a warlock.

However, Schuldiner was struggling with brain cancer and was unable to be involved despite the efforts of Grohl and others to raise funds for his medical treatment.

[11] Grohl also attempted to get Slayer's lead singer Tom Araya on the album, but he was unable due to scheduling conflicts.

[13] Grohl mentioned he and Sweeney had discussed and considered a lot of different singers, including the retired Jeff Becerra of Possessed, Chuck Billy from Testament, Pantera's Phil Anselmo, and the vocalists from Kreator, Destruction, Hirax and Candlemass.

"[9] So Grohl's friend Pete Stahl, with whom he had played in Scream and was then in the band Goatsnake, suggested the label of his bandmate Greg Anderson, the smaller metal-based Southern Lord Records.

Southern Lord released a double A-sided single, "Centuries of Sin/The Emerald Law" in a limited edition of 6,666 on 7" vinyl only.

Rolling Stone declared it as "the year's first great metal album," while Blender reported, "Unlike similar records... this has a unity of aesthetic purpose, a competitive wallop, even (kind of) a seriousness."

He notes, "For a lark, it aims for (and hits) a few bull's-eyes, including the whiplashing 'The Emerald Law' and the post-apocalyptic death march 'Ice Cold Man'."

However, Browne comments how the mystery and thrill of vintage metal bands is "largely gone" with many lyrics on Probot sounding "more amusing than menacing" and even "unintentionally funny."

Adrien Begrand of PopMatters describes it as "One of the coolest ideas for an album in a long time, Grohl has put together a record that not only serves as a sincere tribute to the metal and hardcore bands of his youth, but features all his favorite vocalists as well."

Awarding a 4/5 rating, Allmusic's Alex Henderson emphasizes the wide variety of genres featured on Probot and adds, "Whatever the style of metal that he is embracing, Grohl's drumming is passionate throughout this fine album, which is as rewarding as it is unpredictable."

"[4] The song bears strong resemblance to Lemmy's style and was considered "a terrific Motörhead clone" by Adrien Begrand of PopMatters.