Is the Nikon d3100 capable of doing these pics?

Is Nikon d3100 capable of doing these kind of pics?

http://www.smashingmagazine.com/2008/09/07/35-brilliant-examples-of-rain-photography/
http://prestigeportraits.com/gallery.aspx

If not, is it close? I have the 18-55 mm lens will that work?

Of course -- it just depends on whether you as the photographer knows how to work the camera.

(although some of the photos in the second link would require a macro lens)

Some use a longer focal length. The 55-200mm might work. Some have very shallow depth of field. The 85mm f1.8 would probably be best for duplicating the effect. Some are very close. The Micro Nikkor 40mm AF-S DX f2.8 or the Micro Nikkor 60mm AF-S f2.8 could be good.

I agree, do you know how to operate a dslr to get those results. They're nice shots and who ever took them knew what he / she was doing.

First of all Its very great you have taken this camera!
Well it entirely depends on your skill no matter the optics.take a Nikon 70-300 lens(real cheap!)