iptables is a packet filter, or firewall in common terms. And yes, that is what you need in order to allow or deny traffic from reaching your server. There’s no “securing” packets per se, as iptables does nothing to the packet content (it does not encrypt/decrypt).

iptables management is a faily large subject, I suggest you get yourself some reading material.

This is a good starting primer :
https://danielmiessler.com/study/iptables/