Please Help Me Figure This Movie Out

I cannot remember what movie this was from my childhood. I will describe to the best of my knowledge. I know this is an 80s movie MAYBE very early 90s. There is a mark of some sort in the back of people's neck to tell they are monster's or possessed. Also, a boy puts a penny in a slot of a monster's head(?) to shoot out a laser. It is killing me not to remember this darn movie. I tried google and other search engines. PLEASE HELP ME OUT SOMEONE!!!

 

hmmm......some of it sounds familiar....is that all you can remember?

 

that is all i can remember. The penny that the boy puts in...it has to be copper, that is the only way it works. They might be in a cave of some sort. PLEASE HELP

 

THE SEARCH IS OVER!!!!!!!!!!!! i found out what movie it is. Invaders from Mars