These FTSE giants have surged in Q4! Can they keep it up?

Copper giant Antofagasta (LSE: ANTO) has seen its share price explode this quarter, the stock now trading at a 35% premium to levels seen at the start of October.

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The commodities giant had already booked handy gains in the run-up to last week's US election. But the success of President Trump -- and consequent hopes of significant infrastructure spending -- has injected a large dose of jet fuel into the commodities sector, and with it Antofagasta's share price. The business struck 17-month peaks of 724p per share just today.

Surging copper values at the London Metal Exchange helped propel Antofagasta's share price over the past week, with three-month futures climbing above $6,000 per tonne at one point, also the highest since last summer.

But market sentiment remains extremely volatile, and the red metal was recently dealing back around $5,600. Buyers have taken a step back as caution has emerged over the reality of the newly-elected President's plans leaving the drawing board.

And while Chinese factory data has ticked higher of late -- industrial output rose 6.1% in October, data showed just today -- the protectionist agenda put forth by President-elect Trump could see manufacturing in the country take a hefty whack, and with it commodities shipments into the country.

Copper values desperately need demand indicators to remain robust, as miners the world over flood the market with extra supplies. Antofagasta itself saw production shoot 8.7% higher during July-October as its Antucoya asset hit full production.

There are clearly a number of issues that could send metal prices shooting lower again. But I do not believe Antofagasta's share price factors in these issues -- a prospective P/E ratio of 39.7 times is well above the FTSE 100 average of 15 times.

Given that the copper sector's fundamentals remain on shaky ground, I reckon such a heavy multiple leaves Antofagasta in danger of a severe retracement.

Make a deposit elsewhere

Although the trading outlook for Britain's listed banks remains as murky as ever, investor demand for Royal Bank of Scotland (LSE: RBS) has shot through the roof in recent weeks. Indeed, the firm enjoyed a 17% share price rise during the first half of the current quarter.

I see no justification for this heady spurt, however. RBS swung to a £469m loss between July and October from a £940m profit a year earlier, the firm announced late last month, with restructuring costs and misconduct issues still smacking the bottom line -- the bank set aside £425m during the third quarter to cover the mis-selling of residential mortgage-backed securities.

But colossal costs are not RBS's only problem, of course, as aggressive asset shedding hinders the firm's ability to generate revenues expansion. These divestments are particularly problematic as UK GDP looks likely to deteriorate in the months ahead, and the Bank of England appears on course to keep interest rates around record lows to support the economy.

I believe a forward P/E ratio of 16 times is far too heady given RBS's multitude of woes.

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Royston Wild has no position in any shares mentioned. The Motley Fool UK has no position in any of the shares mentioned. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.