Where I live two 16 year olds can get married if their parents consent (I don't know who would) But these teenagers think that their current boy/girlfriend is their "true love". The truth is that first relationships never work out. Or the second. That's the point, you go out with someone to see if they're the right person- but you don't know what kind of person you want until you've had experience. Studies have shown that people who marry at 20 have higher divorce rates than those who wait. Imagine getting married at 16 and spending the rest of your life (which could very likely be a good 80 years or so) with the first person you ever dated. They are too young to know the lasting effects of marriage.
16 is too young to get married. People should wait until they are 18. There is a legal limit because kids are too immature if they are too young. They should have some experience before they make such a big commitment. At 16, kids have not eve finished high school, and they cannot legally work full time jobs.
If we, as a society have decided that a child becomes an adult at age 18, we need to stick to that for everything. Marriage is a union for adults, not for children, so if a 16 year old is still a minor it makes no sense to allow him or her to enter into a binding union that they aren't ready for.