In no particular order:

Eagles - The Last Resort
My absolute favourite song of all time. I've said more than enough about it on here over the years but no other form of art or anything similar has ever had such an impact on my life. Sadly that impact was probably to make me more of a sceptical nihilist sod than I was before, but in all seriousness the political and social messages within it are quite dear to me. The verse beginning 'Who will provide the grand design...' is just as good as any prose I have ever read in my life.

Judas Priest - Breaking the Law
A complete contrast, but my second favourite band behind the obvious. I forst heard this song on Jackass and a quick Google search left me hooked on the band. Though they have covered quite a vast array of metal types and messages over the years, they are the quintessential heavy metal band there ever will be, and as a teenager growing up their music and their message made me feel accepted (God knows by who) and OK with myself when very little else in the world did. BTL is by no stretch my favourite Priest song, and most of their early and mid-80s catalogue is far more impressive as an example of their ability, but this song is the first I ever heard of them, and as such probably has to be my choice!

UFO - Doctor Doctor
Hearing this for the first time was like being struck by lightening, sizzling off slightly and then being struck again several more times. I would put it forward as the perfect rock n' roll song - the calm intro building up into the cutting riff and lyrics so well constructed that you can sing in perfect time with the vocalist for most of the song; it is the very essence of what hard rock music is built on. Also a reasonable demonstration of the abilities of one Mr. Michael Schenker, for me one of the most underrated rock guitarists of all time. Watch any live performance of this (particularity back in the day) and it just personifies everything people think rock n' roll is.

Kiss - God Gave Rock And Roll to You II
A special mention to Argent who originally did this, but Kiss absolutely nailed the cover. It shares the same eager, hedonistic message as, for example, Take It Easy does, but I think much in the same way as I feel with Judas Priest's work, it's one of those songs that makes you feel like you belong to something and that no-one can take away from you, and again that helped me growing up and still helps me now in those odd occasions that you have a really bad run of it.

Black Sabbath - War Pigs
This song did as much for hard rock and heavy metal as any other song ever has for its respective genre. I think that much like The Last Resort it's probably shaped my politics and personal views more than anything, but it is still such a good example of what Sabbath were capable of as a band and how good a lyricist Geezer Butler is. Lines like 'Politicians hide themselves away, they only started the war / Why should they go out to fight, they leave that all to the poor' were very accurate for a lot of what had gone on in the world and rather prophetic of what would lie ahead. There are very few hard rock songs that create relevant commentaries on the likes of war and unrest (most of the time it's usually hypothetical destruction of mankind!). All that said however, the repetition of 'masses' in the first two lines annoys me greatly