Mónica Sierra began her professional career in Havana, Cuba, at the age of three. At six, she recorded the iconic lullaby "La Calabacita," which became a bedtime anthem for Cuban children. As a child, she was a lead singer in a prestigious kids' group, making regular TV appearances. She studied at Havana’s Amadeo Roldan Conservatory and, by 16, was touring internationally with the all-girl tropical band Azucar.

In 1999, Mónica immigrated to the United States and quickly became a lead vocalist for a band at "Café Nostalgia," a renowned Latin club in Miami. Her behind-the-scenes work in the music industry involved collaborating with legendary artists such as Emilio and Gloria Estefan, Jorge Villamizar, and Luis Enrique. She also worked on the All-Star Celia Cruz tribute band at the 2003 Grammy Awards, earning her membership in the American Society of Composers, Authors, and Publishers (ASCAP).

Mónica also spent eight years as a singer on popular TV shows like “Seguro Que Yes” and “Esta Noche Tonight” with Alexis Valdés, and “El Vacilón” with Enrique Santos and Joe Ferrero. Currently, she is the producer of the Spanish versions and voiceovers for Pinkfong, the company behind the global sensation “Baby Shark,” which has garnered over 130 million views and nearly 6 million subscribers on its Spanish channel.

Mónica is Machaka’s lead vocalist and songwriter, a true jewel in the band's crown.