His paternal grandfather, a Spaniard from Ávila who was born in 1916, emigrated shortly after the Second World War, going to Brazil first before settling in Honduras.

[2] Lopez signed with Top Rank in October 2016,[8] and made his debut on the undercard of the Manny Pacquiao vs. Jessie Vargas fight in November of the same year.

[9] After compiling a perfect 10–0 record, he announced himself to the world stage in December 2018 by beating veteran Mason Menard with a knockout of the year candidate.

[11][12] Lopez's winning streak continued, improving to 13–0 with a fifth-round knockout victory against former world title challenger Edis Tatli on April 20, 2019, on the undercard of Terence Crawford vs. Amir Khan at Madison Square Garden, New York City.

The fight marked the first time Lopez had gone 12 rounds in his career, and he was awarded a unanimous decision victory with scores of 118–110, 118–110, 119–109, setting up a clash with IBF champion Richard Commey.

Lopez won the IBF title in spectacular fashion after connecting on Commey with a big right hand, and finishing him with a second-round technical knockout.

[16][17] In September 2020, Lopez agreed to fight unified WBA (Super), WBO, and The Ring champion, Vasiliy Lomachenko, on October 17 at the MGM Grand in Las Vegas.

With no live audience, Lopez defied the odds with a stunning upset victory as he beat the highly-regarded Ukrainian by unanimous decision to unify the lightweight division and maintain his unbeaten record, with the judges' scorecards reading 116–112, 117–111 and 119–109.

Despite returning the favor by knocking down Kambosos in the tenth round, Lopez ultimately lost the bout via split decision.

In his first bout at the weight class on August 13, 2022, he successfully rebounded from his loss against Kambosos by defeating Pedro Campa via seventh-round technical knockout after a dominant performance.

[40] On February 8, 2024 in Las Vegas, Lopez defeated Jamaine Ortiz by unanimous decision and made the first successful defence of WBO light welterweight title.