Whats the stuff on the door drain lip?

[j5ball]

68 Pontiac Lemans. There is some filler/caulk/?? that is on the outside of the car between the door drain lip on the top of the car. Its just a bead that runs along the outside of the door lip. Mine has now hardened and looks like plumbers putty after its hardened. What is this stuff? What purpose does it serve? Do I need put something back to replace what I took out?

 

[melsg5]

Buy some black silicone in a tube to replace the material which acts as a water seal.

 

[j5ball]

Should I prime the area before I put on the silicone or just apply the silicone to the bare metal? Or prime and paint the area then put on the silicone and paint again? What is the proper sequence?

 

[CatSkinner]

Just clean it, make sure there's no rust or flaking paint, if everything looks good, run the bead.