Merritt Island is in the northern part of Brevard County and is surrounded by the Banana River on one side and the Indian River on the other.
Melbourne is Central Brevard and has many different areas such as Suntree,Eau Gallie,Viera,Lake Washington. Close to major shopping OR going out to areas with over acre lots. Melbourne has a eastern boarder of the Indian River.
Palm Bay has a large land mass with plenty of different areas. Plenty to do and shop in the area. Palm Bay is located in the southern part of Brevard County. Like Melbourne their eastern border is the Indian River.
For Merritt Island scan this in your browser : en.wikipedia.org/wiki/Merritt_Island,_Florida
Palm Bay en.wikipedia.org/wiki/Palm_Bay,_Florida