Mallard's interest in music was incorporated into his character and he frequently played music on the show. After finishing Year 12, Mallard chose to pursue acting full-time and he re-joined Neighbours as a permanent cast member in 2016.
He returned the following year for a further 4-month guest stint, while still at school. He had never previously considered acting but this experience made him realise this was what he wanted to do for the rest of his life. He obtained an audition through his modelling agent, which he unexpectedly won. Mallard made his acting debut in 2014 at the age of 15, taking over the role of Ben Kirk in the Australian television soap opera Neighbours for a three-week, six episode guest stint. The band has played in venues around Melbourne, at school music events, and Associated Catholic Colleges' Battle of the Bands competitions. He is a guitarist and singer in punk rock band Enemies Alike. Mallard is a musician and plays the guitar, piano and drums. He featured in several campaigns, including an editorial spread in Yves Magazine. When he was 13, Mallard was scouted by a modelling agent and signed with Vivien's Models. He competed at state and national levels, winning two bronze medals in the team events at the 2012 Victorian National Champions and 5th place in the under-15 National Sabre Championships in 2013.
Mallard took up fencing at the age of ten. He completed the Victorian Certificate of Education (VCE) in 2015, as well as a course in Technical Production. He attended the all-boys school Christian Brothers College, where he was a College Prefect.