#1
I have an ibanez starter guitar which i will upgrade soon, but i want to replace the strings. .

i dont know anything about strings and what features should i look on them to find the best to buy

I love playing stuff of Metallica, Slayer, Avenged Sevenfold, GNR, Steve Vai etc
#3
it depends on what tuning u want to play in, but seeing that u like to play metallica, slayer, a7x and vai, u should stay with light strings, such as 9s or 10s, cuz they all play in standard tuning or drop d, a7x sometimes in drop c#.. the brand doesnt matter, to me at least! good luck man
#4
ernie ball reg. slinky's, or d'addarios, try to get the m steel wound (lol)
Just call me Julius, J, etc.
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