NEW YORK -- American Express (AXP) - Get American Express Company Report has taken a beating, but now the bulls are back. 

OptionMonster's Heat Seeker system detected buying in the May 79.50 calls for 47 cents early Monday morning. The credit-card issuer pushed higher into the afternoon, and premiums soon doubled to as much as $1.05. Volume topped 6,000 contracts, almost twice the open interest in the strike.

That kind of leverage is possible because calls lock in the price where a stock can be purchased. They cost much less than the shares, letting investors profit from rally with much less capital at risk, though they can quickly lose value on a pullback. 

American Express rose 0.91% to $79.70 on Monday. It peaked around $96 last summer, stalled near that level in December, and then quickly skidded under $80. Shares have been trying to hold their ground more recently at the current level, which was an important consolidation area in late 2013. 

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Total option volume ended the session at almost twice the daily average. Calls outnumbered puts by more than 3 to 1.

-- Written by David Russell of OptionMonster.

Russell has no positions in AXP.