The South Korean company describes the Galaxy Alpha as representing a "new design approach".
The firm has previously been criticised for the plastic feel of its handsets at a time when other firms have opted to use materials marketed as having a "premium" feel.
Samsung Electronics saw a 20% year-on-year drop in its last quarter's profit.
It blamed "slow global sales of smartphones".
The company recently lost its status as China's bestselling smartphone-maker to Xiaomi, a local rival, according to the research group Canalys.
Xiaomi's latest handset, the Mi 4, also features a metal-framed build.Xiaomi made a virtue of its Mi 4's metal frame design at a press conference last month
"This is a clear acknowledgement by Samsung that it needed to address some of the criticism that it faced on the Galaxy S5 and deliver a more premium feel," Ben Wood, chief of research at the telecoms consultancy CCS Insight, told the BBC.
"To actually make these devices in the kind of volumes that Samsung needs to deliver them across all its markets is a real challenge, so it's quite remarkable that it's been able to turn this product around so quickly.
"The challenge will be marketing it without cannibalising sales of the S5."'Missed opportunity'
The new handset has a 4.7in (11.9cm) screen, making it slightly smaller than the Galaxy S5.
Its camera also has a lower specification of 12 megapixels, but it benefits from being nearly a fifth slimmer, measuring 6.7mm (0.26in) deep, and is also lighter, weighing in at 114g (4oz).
The move followed several reviews that had praised the Galaxy S5's capabilities while criticising its feel.
Other manufacturers that had already shifted to offering part or full-metal bodied phones at the time included HTC, Huawei, Apple and Sony.
One expert, who tested the Galaxy Alpha before it was formally announced, has doubts about the new device.
"The back is still a plastic cover and it doesn't do enough to compete with the look and feel of the HTC One, for instance," said Francisco Jeronimo, a mobile devices analyst at the research firm IDC.
"This was an opportunity for Samsung, and it's missed it again.
"Unless the Alpha is made very affordable and put in a mid-tier price band, it may have difficulty as the materials don't feel as premium as some of its competitors."Marketing materials for the new handset focus on its design rather than its specifications
A spokeswoman for Samsung said it would announce the device's price and shipping date at a later stage.
The company is expected to unveil the Galaxy Note 4, its latest large "phablet" handset, in Berlin on 3 September ahead of the start of the Ifa tech show.