The French begin the process of picking a new president this Sunday.

Don't care? Well, you should: there's revolution in the air and in an era of political insurgency, this election could not only reshape the nation but also the Western world.

And France has a key role in developing Australia's next fleet of submarines, at a cost of $50 billion.

Voting in France is different to what we've seen recently in the US and what is coming up in Britain, so here's what you need to know.

How does it work?

French presidential elections rely on a two-round voting system.

The first round is happening this Sunday (local time). In Australia, we'll know the results on Monday morning (AEST).

There are 11 candidates on the ballot paper for the first round of voting. That means no-one is likely to get the required 50 per cent for an outright win on Sunday.

The top two candidates after the first round will go through to a run-off vote on May 7.

Normally the only candidates with a chance of finishing in the top two (and making it to the second round) are those from France's two main parties — the Socialists and the Republicans.

But this election is anything but normal. Under the deeply unpopular President Francois Hollande, who had an approval rating of 4 per cent, Socialist support has collapsed and in the final weeks of campaigning it has turned into a four-way race that is simply too close to call.

Three of them are outsiders, two would completely overhaul France's relationship with the world, and the only mainstream contender is under a corruption cloud.

The far-right candidate

Marine Le Pen is expected to make it through to the second round. ( AP: Michel Euler )

On the far-right of the political spectrum is Marine Le Pen.

The leader of the National Front has led the majority of polls in recent months and is considered likely to make it through to the second round.

The far-right firebrand admires US President Donald Trump and Brexit, has courted Vladimir Putin, suggested a "Frexit" referendum and another on the euro currency.

Her chances of calling the Presidential Palace home are considered relatively slim.

That's because all the other major contenders plan to back her opponent if she makes the final two.

But if she defies the odds it will be another dagger in the heart of the liberal world order.

The far-left candidate

Jean-Luc Melenchon has consistently been fourth in the polls. ( Reuters: Robert Pratta )

The other great disrupter is Jean-Luc Melenchon.

The eloquent far-left leader of a movement called La France Insoumise (France Unbowed or Rebellious France) has also threatened "Frexit" and suggested abandoning the euro.

His protectionist economic policies are not far-removed from Ms Le Pen's. Among his ideas are a 32-hour working week, the nationalisation of assets and 100 per cent taxes on personal income over $400,000 euros.

If he and Ms Le Pen were to face off against one another, the race would become even more unpredictable.

Some think it would trigger a financial crisis. At a minimum either candidate could quickly splinter the remaining unity within the European Union.

He has, however, been consistently in fourth place in the polls.

The centrist independent candidate

Emmanuel Macron has emerged as the favourite to win the election. ( Reuters: Stephane Mahe, file )

Uncertainty has seen much of France's political elite coalesce around Emmanuel Macron.

The 39-year-old former investment banker, who served as a minister under Mr Hollande, has never run for elected office.

When he formed his party En Marche, a pro-EU movement that is supposedly neither left nor right, most thought he would finish third or fourth.

Now, he's considered the favourite to become president.

Mr Macron has probably been the biggest beneficiary of the meltdowns in the mainstream parties and polling puts him on almost level pegging with Ms Le Pen.

His supporters speak endlessly about how disillusioned voters have been captured by his ambitious promises to improve health care and education, and boost unemployment benefits, all while reforming the struggling economy.

But his biggest asset seems to be that he's neither from the far-left or the far-right.

Mr Macron's biggest challenge will be getting through this weekend. He's largely untried, untested and doesn't have the party infrastructure of a typical leading candidate, so there's always a chance his support could slip away at the last moment.

Throughout the campaign there's been a lot of focus on his wife Brigitte, who is his former French teacher and 25 years his senior. The relationship is considered unusual, even in liberal France.

The former prime minister

Francois Fillon has seen his presidential campaign rocked by a corruption scandal. ( Reuters: Christphe Archambault )

The dark horse, if that's the right phrase, is the candidate from central casting.

Francois Fillon looks like a French President — the 63-year-old conservative is stylish and has just the right amount of grey.

When he unexpectedly beat former president Nicolas Sarkozy and favourite Alain Juppe to become the Republican candidate last year, most pundits expected he'd win the race in a canter.

Then his campaign was badly dented by a corruption scandal — he's accused of incorrectly paying his wife and children to work for him as parliamentary aides — and ever since, polls have consistently put him in third place.

Despite this, the former PM is still considered a chance, mainly because of his experience.

The French are famous for calling for change only to stick with the status quo. If Mr Macron falters, he could swoop in.

What are the deciding factors?

There are a few to watch out for in the coming days, but the biggest are undoubtedly turnout and which way undecided voters will swing.

If you do a straw poll on the streets of France, chances are you will hear that none of the candidates are good enough.

The country is reeling from repeated terrorist attacks — a shooting on Thursday night (local time), in which a policeman was killed, unfolded as the candidates were midway through TV appearances.

The nation is also struggling with mounting debt and experiencing double-digit unemployment in many areas — so perhaps it's not surprising that voter disillusionment is so high.

Polls suggest as many as a third might not cast a ballot, and as many as a quarter remain undecided.

In a close race that makes things even more unpredictable.

But pundits do expect those factors are more likely to help Ms Le Pen and Mr Fillon because their supporters are more "rusted on" and likely to turn up.

So, what does it all mean?

The result will have major ramifications for the country, continent and potentially the globe.

The head of state in France has enormous power, particularly over foreign affairs.

Also, if anyone but Mr Fillon wins, the country will have an "outsider" as a president — and who probably won't have much parliamentary support.

Parliamentary elections in June usually confirm a newly elected president's mandate.

But Mr Macron, Ms Le Pen and Mr Melenchon don't have the party infrastructure to realistically get a majority and could potentially see their agendas frustrated.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 28 minutes 50 seconds 28 m Lateline special on the French election

The future of France

Widespread voter unhappiness on the streets is also unlikely to go away.

Even if Mr Fillon wins the keys to the palace and a parliamentary majority, he'll have the difficult task of pulling France out of its current slump before the next poll in 2022.

Failure could easily encourage the country to move further towards the political extremes or Mr Macron's independent centre.

It's incredible to reflect that when this campaign began, no-one gave the outsiders a chance. Now, anything could happen.