Weeeeeeeeeell... *thinking hard*... I'm not the best one to tell it, as I don't use to read a lot of metal articles, but I'll make an efford. Sirius ask us, we have to do our best
An article is supposed to be written for some event, like a new CD release or a new gig, so it's ever good talking about that event, of course. But not only this. I don't like the interviews in which there's only Question-Reply-Question-Reply, although sometimes it can be interessant, depending on the questions and the interest of the replies. But I prefer some writting of the author, specially if s/he knows enough about the band and is a good writter. Personal impressions are good, if it doesn't become a "Oh, they're Gods, what a fucking new disc! OMFG!". It gives some personal taste to the article.
I don't know, if I think in something more I'll write here.