As most people who know me know, I am hugely into extreme metal, especially thrash metal and death metal.
I am pretty sure if I ever got married, 90% of the families that showed up to the wedding party would be gone two or three songs in, regardless of the lyrical content the songs had.
For pretty much all parents in my neighborhood that I knew whose children were born around the time I was (I was born in 1985, so we'll say early to mid 1980s, or perhaps up to a couple of years afterward), they despised metal, as well as punk, and even the harder side of classic rock radio.
I can see where thrash metal such as Slayer, Sepultura, Kreator, and Dark Angel would be too much for them to handle. As for death metal, don't even get me started.
To a lesser degree, I can understand groove metal (or "post-thrash", as it's sometimes called), such as Pantera, and the more melodic and accessible bands that are considered thrash metal, such as 1980s Metallica and Anthrax, might be a bit much for a very large percentage of them.
To a lesser degree than that, even the more traditional metal such as Iron Maiden, I could understand being a bit too heavy for a lot of them.
But even the harder classic rock bands, such as Led Zeppelin, KISS, AC/DC, and Van Halen, were considered a huge no-no around the majority of them. Even the men. I could perhaps understand a lot of the women being put off by even the harder classic rock bands (given that hard rock, punk, metal, etc., have predominantly male audiences), but even the men despised bands along those lines. Basically, for the vast majority, the heaviest music they could put up with was closer to Elton John than to even Van Halen, let alone thrash metal.
So if the harder classic rock bands were too much for them to handle, their heads would likely explode if they heard my music. Something like extreme metal certainly wouldn't be played at wedding parties where you hired DJs, though. I would say for almost of them, unless they were provided a playlist and playable versions of those songs in advance, the harder late 1970s/early 1980s rock bands, such as AC/DC and Van Halen, and 1980s hair bands would probably be the heaviest music you might have a chance of hearing. I'd imagine even a wedding party with those bands, let alone most of what I listen to, would have my friends' parents and my parents' siblings flee before you knew it.
(For what it's worth, my parents aren't metal fans by any means, but they don't hate it as much as just about any of their friends and siblings. They can see why I love it, and would rather listen to my music than some other genres.)