Insecure in what way? Like he's insecure about his appearance? Insecure about your loyalty for him? Insecure in his ways of pleasing you?
A friend of mine has a poker face so despite having insecurities he's able to show people that he's confident or "cool" about it (even when he's really not).
As for me, I don't like to bullsh*t my way through life so if I'm insecure about something I just tell the person upfront, because I'd rather be honest than fake it. Less drama that way. But I've been known to say these things in such a nonchalant way that it's like as if the issue is not even an issue to begin with. Like it's whatever for me lol.
I don't know about most guys, but I will tell you why I am insecure, it may help.
I am insecure because of the following reasons:-
I fear being alone
I fear women are not attacted to me
I worry I will say the wrong things and the girl I am with will leave me
I repeat the same things to my current girlfriend like how beautiful she is
I am always thinking about her
I texted her and eagerly wait for the response back. if I don't hear from her I think I did something wrong
I have low self esteem from being bullied at school and never dealt with the issue
I always worry about what she thinks of me
There are many different ways guys can be insecure. Women are very good at picking up on this trait. You understand things so much better than guys do/ If you feel the guy is insecure, your feelings are spot on. It's generally up to the guy to sort himself out, buy that is not an easy thing. I'm still trying, but getting help is not easy,