As a teenager, Serrano traveled 3 times a week from Blanes to the Mini Estadi in Barcelona, where she would train.

She started Barcelona's UEFA Women's Champions League debut the following 2012–13 season, in a 0-3 home loss to Arsenal.

[8] Serrano scored Barcelona’s opening goal in the final matchweek of the 2012–13 Primera División campaign, helping secure their second league title against Athletic Bilbao.

[7][9] On 6 January 2021, Serrano scored in the Camp Nou against Espanyol in the first competitive match played between women at the stadium.

[17] Serrano played one match in qualification for the 2015 FIFA Women's World Cup, subbing in against Romania.

Melanie was part of Spain's squad at the 2015 FIFA Women's World Cup in Canada.

[1] Serrano did not play any matches during the World Cup as Spain bowed out in the group stage of the competition.