With wire I use two knots. For a "closed" knot I use a figure 8. For an open loop I use a jamb knot.

To tie the jamb knot, tie an open overhand knot about 1" to 1-1/2" from the end of the wire. Pass the terminal end through the hook eye and tie a second overhand knot at the very end of the wire. Pass the closed knot through the open knot and pull the first knot closed. This will cause the two overhand knots to jamb tight together, forming an open loop.

Haven't had any problems with either one of these knots.

Kevin