Different handheld mics come with different polar patterns. While most are cardioid, many are hypercardioid or supercardioid. Which one works best in rejecting feedback depends on the location of the mic in relationship to any floor wedges or side-fill monitors.
For instance, if you are standing right in front of a wedge, you would want a cardioid mic, but if the wedges were off to the side, or you were very close to a side-fill, then you would be better of with a hypercardioid pattern.
The other factor is knowing how to use parametric EQ to notch out likely feedback frequencies. I've been on the road with some top live engineers who EQ the wedges to the point where you can lean over and point the mic right at them, and they still won't feed back!