Provided is an ethylene copolymer having 40 wt. % to 70 wt. % of units derived from ethylene and at least 30 wt. % of units derived from at least one α-olefin having 3 to 20 carbon atoms and has the following properties: (a) a weight-average molecular weight (Mw), as measured by GPC, in the range of about 50,000 to about 200,000 g/mol; (b) a melting point (Tm) in ° C., as measured by DSC, that satisfies the relation: Tm>3.4×E−180 where E is the weight % of units derived from ethylene in the copolymer; (c) a ratio of Mw/Mn of about 1.8 to about 2.5; (d) a content of Group 4 metals of no more than 5 ppm; and (e) a ratio of wt ppm Group 4 metals/wt ppm Group 5 metals of at least 3. Also provided are methods for making an ethylene copolymer and compositions comprising an ethylene copolymer.