[arch-general] iptables forward policy

Good day, I'm currently configuring a router. I'm setting the default policies to DROP in the INPUT OUTPUT AND FORWARD chains. I'm thinking of setting the default FORWARD policy to ACCEPT as my default INPUT policy is DROP and unless there is a valid FORWARD rule for a given port the packets wont go anywhere. I'm I right on this? or could someone deliberately setup a packet to be forwarded from my router to my lan? all I could find on google was one similar question with no answer :( Thanks