Just listen to tons of styles..classical, jazz, latin, rock, pop, anything can add little bits that you can incorprate into your playing. even if you're not into those styles, listen to a song or two and try and emulate techniques that the guitarist (or any musician for that matter) uses.
You can still use those in metal, just try to find parts that you like.
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You need to douse it in a 20/30/50 ratio of mustard/ketchup/horseradish and stroke it as fast as you can untill the mayonaise squirts out. Then consume.
Listen to Bach and Paganini. Seriously, it will give you a new perspective on melody but don't be like Malmsteen and only listen to them, mix some genres.
yh i have had the same problem mate, i've been doing progressive death/black metal mixed with celtic folk music.

seriously just give loads of different types of music a try and see what works with your music

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