ものなら・
Two different "if"s, told apart by the verb in front. After a potential verb, "if I only could": you doubt that it is possible. After a volitional form, "if you so much as…": something terrible follows.
after a potential verb
If only I could, I would see my late grandfather once more.
after a volitional form
Be so much as a minute late, and the teacher gives you a terrible scolding.
If I only could
Potential verb + ものなら
会える, 戻れる, できる. A wish usually follows: たい.
If you so much as
Volitional form + ものなら
言おう, 遅れよう, しよう. A bad result follows, never a wish. In conversation both are もんなら.
After a potential verb: if I only could
You would love to, and you don't believe you can: nobody changes the past or meets the dead. It is said with longing or regret, in conversation as much as in writing. The same verb often comes around again: 行けるものなら行きたい.
If I could change the past, I would make that day's choice again.
If only I could, I would scrap this decision and start again.
できるものなら stands by itself: "if only I could".
If I could take that pain in your place, I would.
What a parent says beside a sick child.
If I could do it over, I'd start again from my first year of college.
ものなら or たら?
If I can get the day off, I'd like to.
It may well be possible.
If only I could take the day off.
You don't think you can.
A dare
With てみろ after it, you dare someone to do what you are sure they can't.
Go on, then. Do it, if you can.
When もの is just a thing
Anything will do, as long as it is something I can eat.
もの is a thing here. 何でも, "anything", gives it away.
After a volitional form: if you so much as
One small step brings a result out of all proportion: fury, ruin, a fall. 一言でも (even one word) or 少しでも (even a little) often comes in front. It is mostly written. In conversation it tells, with some exaggeration, how strict or how dangerous someone or something is.
If he so much as mentioned that fact at the meeting, the whole company would be in an uproar.
Put one foot wrong, and you could fall all the way to the bottom of the ravine.
My dad is strict. If I'm so much as five minutes past my curfew, there's hell to pay.
The volitional here is not "let's" or "try to". It only supposes, so the verb can be something nobody chooses.
If the pressure in these old pipes rose even slightly, they could burst.
Close neighbours
A plain supposition, likely or not, with no longing and no alarm in it.
If we were to go to Kyoto, when would be good?
Other forms built on もの
というものだN2
"That is what you'd call …": a verdict.
Helping each other when things are hard: that is what friendship is.
"It's not simply that …": one thing alone doesn't settle it.
It's not as if saying sorry is all it takes.
ものがあるN2
"There is something … about it": a quality that strikes you.
There is something about her singing that moves people.
"I'd love to", "I do wish they would": a wish said with feeling.
Just once, I'd love to see the northern lights.
"Isn't there some way to …?": you wonder, hoping or worrying.
This heat: can't something be done about it?
Check yourself
1Which one fits?
子どもの
Choose an answer to see why.
2Which one fits?
部長の
Choose an answer to see why.
3A friend at work says this. What do they think?
帰れる
Choose an answer to see why.
More sentences
If I could choose my life over again, I would take a different path.
If I could go back to that day, I would choose different words.
If I could wipe that scene from my memory, I would.
If anyone so much as leaked this information, the whole company would lose people's trust.
If even one of these supports gave way, the whole roof could come down.