She played the lead role in the Nickelodeon television series 100 Things to Do Before High School (2014–2016), and went on to feature in the films Transformers: The Last Knight (2017), Instant Family (2018), and Sicario: Day of the Soldado (2018).

[4][6] Merced has stated that Spanish was her first language, and she struggled with English when she first started grade school,[6] adding that she considers herself more Peruvian than American.

She was a Judy Garland fan, so her parents, in an attempt to distract her from the loss, encouraged Merced to audition for a local production of The Wizard of Oz.

She attended the Fairmount Performing Arts Conservatory, led by Broadway producer Fred Sternfeld, who tried to persuade Merced's mother into taking her to New York to pursue auditions.

[21] In 2018, Merced had a major role in Sicario: Day of the Soldado, playing the daughter of a drug cartel head,[22][23] in a performance lauded by critics.

The New Yorker's Anthony Lane wrote "Moner is terrific, and her character’s fortunes can be read in her eyes—blazing to begin with, as she scraps with another girl in a schoolyard, but dark and blank by the end, their youthful fire doused by the violence that she has seen.

[35] On May 22, 2020, Merced released her debut EP, The Better Half of Me, through Republic Records[36][37] and was named one of Billboard's top 15 new Peruvian artists to listen to in July 2020.