IIRC, there are three types of irony:
- Verbal (as in, sarcasm/satire) - for example, saying “Oh, wonderful” when in fact something really horrible has just happened
- Situational - Generally, your plans going wrong in the worst way possible. Murphy’s Law covers this part, but also simply unfortunate coincidences that tend to suck. Irony is kind of funny, even if it happens to you.
- Dramatic - Someone else (typically, the audience in a play) knows what’s going to happen to you, but you don’t yet.
A good example is the story The Gift of the Magi. The husband sells his watch to buy his wife a beautiful set of combs, and the wife sells her hair to buy her husband a gold watch chain. It’s situational irony - they each sacrificed the very things that the other was getting gifts for, but it’s also dramatic irony - they didn’t know what the other was planning, but the reader does.
Incidentally, does irony have a negative denotation, or does it just have a bad reputation?
So, back to the song:
“10000 spoons when all you need is a knife” - well, it might make the mark (because part of Murphy’s law is “you never find something when you need it”), but it definitely would pass the irony test if you had stocked up on your silverware fear of not having enough spoons, but then the day you need a knife you can’t find a single one.
“Guy who is afraid to fly getting on a plane which then crashes” - sort of ironic, because it did justify his fears (if he lived through it). Probably would have been more ironic if an airplane pilot who had a pristine record went on his first commercial flight that he himself didn’t have to fly - and then promptly found himself on a short trip back to the ground.
“Rain on your wedding day” - it’s already been covered. As is, it’s just unfortunate, not ironic. (Again, more Murphy’s Law than pure irony.)
“Life has a funny way of…” - the bad stuff happening on good days is definitely at least Murphy’s Law, and certainly would have ironic moments. Good fortune genuinely isn’t considered irony, unless it happens to someone you’re planning nasty things for. (Like, for example, there’s a Grimm’s Fairy Tale about a king who tries to off a boy by having him deliver a note saying “have this boy killed”, but some ruffians take pity on the boy and change the note to “marry this boy to the princess”, which is exactly what the king didn’t want to happen. Irony for the king, but not the boy.)