MSL UK co-CEO James Parsons will continue to oversee the firm's 15-strong corporate team following Metcalfe's departure later this month, and he told PRWeek he would shortly be appointing an MD for the division.
Clients of the team under Metcalfe have included law firm Gowling WLG, P&G, Fujitsu and Netflix, as well as AkzoNobel, as part of a global contract awarded last year.
He said: "Blair moves on with our blessing - he joined at a time when we were turning the business around and reshaping corporate. We're sad to see him go, but it's very amicable."
Parsons and his fellow co-CEO Jason Frank took up their roles in September 2014.
Metcalfe joined at the start of 2016. Prior to arriving at MSL, he had spent seven years at Ogilvy PR UK, latterly as head of media and entertainment.
Metcalfe is setting up a new venture called The Agency Partnership, which will be headquartered in London but has international ambitions.
He said: "In bringing together a collective of communications marketing experts, but also in establishing an international partner network, we are able to deliver global, regional and local communications; led from London. Crucially, we can establish a service model that brings together the right team at the right time, whilst avoiding picking-up any of the excess baggage of fixed networks."
Metcalfe, who is also a PRCA Council member and Young Lions judge, went on to say: "Building-up MSL’s Corporate practice from late 2015 to become a PR-led team achieving huge growth and success by 2018, is something that I am immensely proud of. I know that I am leaving a great team behind, and that they will continue on that journey; delivering for clients, new and old."