I gave the quickest examples I could find. I can find numerous other references to the poppier nature of Van Halen on all three sources. And while I agree a source is not often 100% reliable, especially one relying on opinion...3 major sources IS. Especially given they're frequently used accross Wikipedia. Van Halen began as a hard rock band with a heavy metal edge at times...but "Dreams" is definitely a pop rock song. Generally the 1984 album is considered the one where the band became poppier, and in the Sammy Hagar era that really took root. 

Power ballads are the most common pop rock crossover out there.

Oh, and a lot of their covers were poppy songs anyway, like You Really Got Me.

I have some more stuff below, but first, look at this. I doubt you can be bothered to listen to them all, but listen to the first 30 seconds of each:
http://www.youtube.com/watch?v=83eMZZ518xE

http://www.youtube.com/watch?v=5wAlbH5v7OA

http://www.youtube.com/watch?v=YfTwMgGBARM

http://www.youtube.com/watch?v=mBDC2m7Qxxk

http://www.youtube.com/watch?v=4oZhSWhJ7lM

http://www.youtube.com/watch?v=Lit8LbTQQZo

http://www.youtube.com/watch?v=2zwoIW9bEa4

http://www.youtube.com/watch?v=X1w5IvHSPec

http://www.youtube.com/watch?v=pQ-5nwt-j9E

As a side note, Bon Jovi's first two albums are definitely glam metal - they made their name as part of the glam metal scene. Which is pop metal by the way, making it hard to classify. They went the commercial side of things and moved away from metal. Guns N' Roses, again, sleaze rock. Something that formed from the ashes of glam metal - but Guns N' Roses were among the first. So the line between sleaze and metal blurs with them. They ARE the crossover point. AC/DC I'd not call metal, and I think KISS had a few metal songs but don't really count...but they are heavily disputed the two of them. Opinions on either carry little weight. 

Wikipedia has several definitions for pop rock: "Pop rock is a subgenre of rock music that uses "catchy" pop style, with light lyrics over top of "guitar-based" songs". I would say that sums up some of Van Halen's stuff to a t. "they only use pop hooks or synths to appeal to both a hard rock and pop audience from time to time"? Have you heard their latter-day singles? 

"Sure they used synth, and sure they've used pop hooks, but haven't countless other hard rock and heavy metal bands done so?"

It most frequently happened in glam metal. Which is aka pop metal. Glam metal is a genre a lot of people wanted to attach to Van Halen, personally I think just because something's pop rock and heavy metal at different times does not make it pop metal. Hence my desire to keep pop rock - the comparisons to glam metal are made obvious that way. It's hard to ignore them, but also impossible to just call it glam metal.