Security is a huge and varied industry. in my time doing security, i've done:

-concierge/customer service sitting at a desk all day directing people
-mall-esque retail space where I confronted people a lot but couldn't lay a hand on them
-concert security where I arrested and grappled with people constantly
-stood at the front door of a store and did nothing while looking "tough" (worst job ever)
-worked in an apartment complex kicking out trespassers and breaking up parties
-worked executive protection in a suit and tie
-worked as a first aider in warehouses and special events
-worked in a hospital which involved everything from arresting trespassers to restraining patients to moving bodies

Most guys are working "warm body" type positions, doing guest services, watching cameras or doing basic patrols and calling police or their boss for any real problems. but if you are ambitious and able to learn, theres lots of places to go in security.