MNM debuted on WWE's SmackDown! roster in April 2005. Consisting of Johnny Nitro and Joey Mercury, along with their valet Melina, they made their debut during Carlito's interview segment Carlito's Cabana, where they interrupted an interview between Carlito and Rey Mysterio, and attacked Mysterio. This provoked a feud between MNM and Mysterio and his partner, Eddie Guerrero, over the WWE Tag Team Championship. Two weeks later, in their debut match on the SmackDown! brand, they defeated Mysterio and Guerrero to win the WWE Tag Team Championship after Guerrero refused to tag into the match. While Nitro and Mercury held the championship, Melina was placed in an angle with Heidenreich. She publicly mocked him and was the impetus for an attack on him by Nitro and Mercury. In July, MNM were scheduled to face Heidenreich in a two-on-one handicap match, but attacked him before the match started. Road Warrior Animal saved Heidenreich from the attack and as a result, Heidenreich and Road Warrior Animal challenged Mercury and Nitro for the WWE Tag Team Championship at The Great American Bash. MNM lost the match and the championships to Heidenreich and Animal at the event.
The loss of the WWE Tag Team Championship was seen as "bad publicity" by Melina, so she introduced Jillian Hall, a storyline spin doctor to repair their image. Hall got them a cover article in SmackDown! magazine, and began to introduce the team before and aid them during matches. In September 2005, Hall left the group to join John "Bradshaw" Layfield (JBL), who had lost a match to Rey Mysterio.
On the October 28 episode of SmackDown!, Mercury and Nitro were placed into a tag team title fatal four-way match against the teams of the Mexicools (Super Crazy and Psicosis), William Regal and Paul Burchill, and the WWE Tag Team Champions Legion of Doom 2005 (Heidenreich and Road Warrior Animal). During the match, Mercury and Nitro were able to perform the Snapshot on Heidenreich to win the championships for a second time. MNM successfully defended the championships against Eddie Guerrero and Batista on the November 4 episode of SmackDown!. In December, they began a feud with the Mexicools, who earned the right to face MNM at Armageddon for the WWE Tag Team Championship. Before Armageddon however, on the December 16 episode of SmackDown!, MNM lost the WWE Tag Team Championship to Batista and Rey Mysterio. A storyline was begun before the match, where Melina attempted to seduce Batista into forfeiting the match. The storyline played over to the December 30 episode of SmackDown! when, before MNM invoked their rematch clause, Melina held a press conference in the ring where she claimed that Batista had sexually harassed her. During the tag team match, Mark Henry aided MNM in winning back the WWE Tag Team Championship. The following week, MNM defeated Batista and Mysterio in a steel cage match to retain the championships, with Henry's aid. Henry was only with the group a short time before his contract was sold to Daivari in storyline. They went on to successfully defend the championships against The Mexicools and the team of Matt Hardy and Tatanka in early 2006.
In April 2006, MNM were placed in an angle in which they found themselves in a losing streak against the team of Paul London and Brian Kendrick. In non-title tag team matches, singles matches, and even a six-man tag match, London and Kendrick defeated the duo every time. At the Judgment Day pay-per-view in May 2006, MNM lost the tag team championships to London and Kendrick. After the match, Nitro and Mercury started brawling, disbanding the group. Later that night, Melina lost a singles match against Jillian Hall and after slapping General Manager Theodore Long in anger, she and Nitro were fired from the SmackDown! brand in storyline.
After the team split, Nitro, alongside Melina, was quickly placed into the Intercontinental Championship picture, winning the title twice. In November, Mercury returned to WWE, reuniting MNM to answer an open challenge put out by The Hardys (Matt and Jeff) for the December to Dismember pay-per-view. At the event, MNM lost to the Hardys. MNM and the Hardys met again at Armageddon as part of a four-way ladder match, which also included the teams of Dave Taylor and William Regal and Paul London and Brian Kendrick. During the match, which saw London and Kendrick retain the WWE Tag Team Championship, Mercury was legitimately injured when he was struck in the face with a ladder, necessitating a trip to the emergency room where his broken nose received fifteen stitches. The facial injury was worked into the angle, and when Mercury returned wearing a protective covering on his face, the rivalry between the teams intensified with MNM actively seeking to injure one or both of the Hardys, even going so far as to attack and perform a Snapshot on Matt on exposed concrete following a match. MNM lost to The Hardys at the Royal Rumble, and again at the No Way Out pay-per-view in February, which concluded the feud.
After their feud with the Hardys was over, Nitro and Melina continued to team on Raw, while Mercury wrestled in singles competition on SmackDown!. On March 26, 2007, through WWE's official website, it was announced that Mercury had been released from his contract.
Melina and Nitro's association began to fizzle out when Melina became the WWE Women's Champion and began garnering attention as a singles performer.