Metrosideros polymorpha var. incana is a shrub or tree that can reach heights exceeding 30 meters. The trunks typically ascend straight, occasionally originating from two or three shoots from the same rootstock. The bark is gray, shedding in flakes or strips, and the branches are stiff and more or less ascending, appearing either terete or angular when young. The leaves are simple and opposite, with blades that range from obovate to ovate or elliptical-oblong. The apex of the leaves is usually obtuse, though it can sometimes be acute, and the base ranges from cuneate to cordate. The leaf surfaces are pale grey and tomentose on both sides, though older leaves may become glabrous on the upper surface. Margins are flat, and several raised veins radiate from the base. Petioles measure between 6 and 12 mm, and stipules are typically vestigial or absent. The flowers occur in inflorescences of 2–5 pairs of cymules featuring woolly pubescent peduncles that are 7–18 mm long and 1–3 mm wide. Bracts are broadly ovate to suborbicular, measuring 5–10 mm long and 3–5 mm wide. The flowers, which can be red, pink, or orange, are perfect (bisexual) and actinomorphic (radially symmetric). Pedicels range from 1-5 mm in length and 1–2 mm in width, and the hypanthium measures 3–7 mm in height and 3–8 mm in width. Sepals are rounded to triangular and covered in a white-woolly texture, with a calyx extending 5 mm, including the lobes. Petals are oblong, either tomentose or glabrate, and feature ciliate margins. Stamens extend 1–3 cm, and the nearly superior ovary leads to a 1.3–3 cm long style. The fruits are capsules that maintain a grayish woolly appearance, slightly included to exerted, with a fruiting hypanthium measuring 3–8 mm both in length and width and are either pubescent or glabrous. It is found in shrublands and mesic to wet forests between 100-1500 meters.