Not quite so. The metal frame absorbs the phone’s internal heat and raises the temperature of the body when the internals overheat. Someone complained in a forum that his Galaxy S7 edge suffered a cracked screen due to the abnormal heat produced by the battery while charging.
Android authority has conducted various tests on the handset in numerous cases to see if the phone’s temperature rises abnormally. The first test is the 4k recording test. 4k recording puts significant stress on the phone’s internal and 10 minutes of video is captured and temperatures are compared before and after the tests. S7 edge and S7 saw a temperature rise of +4.50° and +4.90° respectively. The nexus 6P saw a rise of just +1.73.
When the phones were put through the full HD video tests for 30 minutes, the S7 has seen a steep temp rise of + 5.07 but the S7 edge performed reasonably well with a temp rise of + 3.27.
Other cases such as gaming test have shown that the phones perform excellently and are mostly cool.
But one thing is for sure, the handsets heat up abnormally while the camera is involved. Some of the other phones that performs better than the S7 duo are the Nexus 6P, LG V10, Note 5.
on the whole, the S7 duo heats up reasonably but aren’t considered as overheating devices.