2014–2021: Portuguese film and television Melchior started her career in 2014 with the role in
telenovela ''
, where she starred for 316 episodes and, subsequently, in 68 episodes of teen drama Massa Fresca (2016). Her breakthrough came with her first leading role as Cláudia Andrade for 221 episodes of the award-winning Portuguese telenovela Ouro Verde (2017),'' establishing her as one of Portugal's most promising young actresses. She also participated in other Portuguese film and television productions, such as telenovelas
A Herdeira (2018),
Valor da Vida (2018) and ''
(2021) and feature-length films The Black Book (2018) and comedy drama Parque Mayer (2018). Her performance in Mayer
earned her a Sophia Awards nomination for Best Actress. After a representative from the United States saw the trailer for Mayer
, they offered to represent her, prompting her eventual move to pursue roles abroad. She also provided the Portuguese voice for Gwen Stacy in Spider-Man: Into the Spider-Verse,
earning recognition among the comic book fan community in Brazil.'' Melchior as Cleo Cazo marked the first portrayal by a Portuguese actress in a
DC Extended Universe film. Gunn described Melchior as "the heart of the film." Critics identified Melchior as the film's standout, describing her as "luminous", "wonderfully guileless", and "the film's secret weapon." In March 2022, she joined the cast of the tenth
Fast & Furious film titled,
Fast X, with
Vin Diesel offering her the role after seeing her performance in
The Suicide Squad. In June 2022, it was announced that she would collaborate for the second time with James Gunn in his
MCU film
Guardians of the Galaxy Vol. 3, making her the first Portuguese actress to appear in an MCU film. Gunn is reported to have written the character, Ura, specifically for Melchior. In August 2022, she joined the action film
Road House, a remake of the
1989 film. In 2024, she joined the cast of action comedy
Balls Up, directed by
Peter Farrelly. In August 2025, she starred in the mystery thriller
American Sweatshop; with critics saying that Melchior was underused in the movie. In October 2025, it was announced that Melchior would star in the comedy horror
Anaconda, a remake of the
1997 film, and in the action comedy
Violent Night 2. In 2023, Melchior went to
Paris Fashion Week as a
Balmain's muse. On
International Women's Day, French fashion company ba&sh invited Melchior for their new campaign. ==Activism and advocacy==