[2] The area combines the Belfast, Lisburn, Newtownabbey, North Down, Castlereagh and Carrickfergus districts from before the local government reorganization of 2014.

The area is made up of established towns, their overspill and the general conjoining of settlements as Belfast expands.

Many of these towns were established and important long before Belfast rose to prominence; Carrickfergus, for example, was the Norman capital of the northern part of Ireland until Edward Bruce's defeat in 1318.

[7][8] The recent reclassification of Lisburn as a city does not change its position within the metropolitan area.

In the 2011 UK Census, the distributions of population, religion, national identity and proportion of immigrants within the Belfast metropolitan area, were as follows.