The Brilliant Emerald has apple green eyes and the abdomen and thorax are dark metallic emerald green with a bright bronze sheen. The wings are suffused by saffron, particularly in the female.
In Britain the species occurs in two distinct populations, one in the Highlands of Scotland and the other in southeast England. In Scotland the Brilliant Emerald is extremely local, centred on Glen Affric and Glen Mor, but the populations appear to be strong. There is also a population in Argyll, west of Loch Awe (now several lochs). By comparison the population in southeast England is much larger, including the wealds of Sussex and west Kent and the heaths of Surrey, north Hampshire and Berkshire. In these areas the dragonfly is locally common and appears to be extending its range
Habitats occupied by S. metallica in Scotland and in southeast England are only broadly similar: sheltered, standing or slow-flowing waters usually, but not always, edged with good tree cover. Larvae need a place to hide underwater and ideally need the dark - i.e. shade provided by trees, overhanging banks, etc. Water bodies ideally but not exclusively need to have a soft peaty or muddy substrate, often overlaid with leaf litter.