By heavy metal I mean Slayer, Fear factory Machine head etc?
If so and you have heard of a band called Chimaira and have there older albums then make sure you buy the latest one called “Chimaiara” very very good and worth a listen!
I am so jealous of you getting to see all those bands. Last gig I went to was Chimaira at astoria last year.
Sorry to say this but Chimaiara are awful, I saw them when they supported Raging Speedhorn and I have never seen a band clear the dance floor so quick!
I was into the whole death metal scene a few years back but I’ve been getting into loads of diffrent types of music now that kind of moved me away from all the metal.
Most of the bands I used to like have now split 
Earthtone9 were by far the best band I have ever sceen, but I really regret missing Medulla Nocte who were probably the best uk hardcore band ever!
If you ever get the chance go and see Opeth live, they are very very very good to watch.