The good news: 26 million people were glued to their TV sets Sunday night as heavy metal heroes Metallica gave their genre a rare appearance on network television.

The bad news: A decent portion of their must-see duet with Lady Gaga was sung into a dead microphone; (her vocals were just fine).

But with their Spinal Tap moment behind them, Metallica is heading out on a 23-date North American stadium tour in May in support of their new album “Hardwired ... To Self-Destruct.”

Presumably, all the microphones will work fine.

On Sunday, guitarist and lead vocalist James Hetfield sang the first few verses of “Moth Into Flame” into a dead microphone. Lady Gaga’s vocals into a different mic went off without a hitch, prompting Hetfield to eventually abandon his mic and run over to Gaga’s.

“The one thing my phone blew up about was how awesome it was that Gaga and James were in each other’s face, singing into the same microphone, and the energy and the spectacle came across,” drummer Lars Ulrich said. “Obviously James did not have an easy couple of minutes, but in some way I guess his anger and frustration translated to television.”