He was a co-flagbearer with Denise Boyd at the opening ceremony, when Australia marched under the Olympic flag to protest the Soviet Union's invasion of Afghanistan.

Metzker first showed his international pedigree in the pool at the 1976 Summer Olympics in Montreal, coming sixth in the 1500-metre freestyle and 13th in the 400-metre event.

He had his first international success at the 1978 Commonwealth Games in Edmonton, Canada, winning a gold and bronze medal in the 1500-metre and 400-metre freestyle respectively.

In Moscow, Metzker trailed the great Soviet swimmer Vladimir Salnikov home by some 25 seconds.

Metzker retired from international competition with another gold in the 1500-metre freestyle at the 1982 Commonwealth Games in Brisbane.