The entire metal community is mourning the death of Warrant singer Jani Lane ... including Slash who posted a message saying, "Just heard about Jani Lane. What a shame. RIP man."
Nikki Sixx from Mötley Crue also weighed in ... saying, "I just heard the sad news about Jani Lane. So hard to swallow when people have kids. RIP."
Alice Cooper posted a message calling Lane a "fallen brother." And Bret Michaels from Poison added, "We'd like to offer our deepest condolences to the family of Jani Lane regarding their loss."
As TMZ first reported, Lane died in L.A. yesterday. He was 47.