The thallus of
Metamelanea appears blackish and has a cracked, texture, meaning it is divided into small, island-like segments called . The thallus is composed of densely packed rows of lichenised colonies containing a single-celled
cyanobacterium (blue-green alga) as the . These colonies are surrounded by fungal
hyphae. As the thallus grows, it tends to break up into vertical lobes. The photobiont belongs to the order
Chroococcales and is characterised by a distinctive brown gelatinous sheath, which contributes to the lichen's dark appearance. The
apothecia (fruiting bodies) of
Metamelanea are darkly pigmented and can be either in the thallus or sitting on its surface (adnate). The appearance of the apothecia varies between species. In
M. umbonata, the apothecia protrude above the thallus surface and have a distinctive (having a rounded elevation in the centre) or (convoluted or wavy) shape. When moistened, the of these apothecia appear strikingly black. In
M. melambola, the apothecia remain immersed in the thallus and are difficult to observe when dry. Upon moistening, they become visible as flat, multidivided discs. These apothecia can grow quite large and may appear as clusters of smaller apothecia due to their divided nature. Unlike some other genera in the Lichinaceae, the apothecia in
Metamelanea develop between the lobes rather than within them. This results in the absence of a true (a rim of thalline tissue surrounding the apothecium), despite earlier descriptions suggesting otherwise.
Pycnidia, which are asexual reproductive structures, have been observed in
M. umbonata. These are immersed in the thallus and contain oblong cells that produce small, rod-like
conidia (asexual spores) at their tips. ==Species==