BUENOS AIRES, May 18 (Reuters) - Argentina's stock, currency and bond market trends on Monday.
* The MerVal stocks index .MERV jumped 6.25 percent to 1,528.58 points -- its biggest one-day rise since late November -- buoyed by sharp gains on Wall Street and the purchase of energy and banking shares locally.
* The index is up 20 percent since May 1 and has reached its highest point since early October.
* MerVal heavyweight Tenaris (TENA.BA), which makes steel tubes for the global energy industry, surged 6.55 percent to 53.70 pesos a share as crude oil prices rose.
* On the broad stock market, volume was light at $16.6 million. Of active issues, 62 advanced, 5 declined and 10 were unchanged.
* Prices for government bonds traded over-the-counter in Buenos Aires gained 2.2 percent on average, rising for a third straight session on a fresh wave of speculation that the government could carry out a bond swap to try to lighten this year's debt load.
* Local media and market players are once again discussing the possibility that the government could try to extend maturities on its Boden 2012 paper ARBODEN12=RASL ARBODEN12D=RASL, drawing in investors by offering to pre-pay obligations that come due in August.
* The dollar-denominated 2033 Discount bond ARDISCD=RASL rose 4.2 percent to an ask price of 37.40.
* In formal exchange between banks, the Argentine peso closed 0.07 percent firmer at 3.7250/3.7275 per dollar ARS=RASL.
* In informal trade between foreign exchange houses, as measured by Reuters, the peso strengthened 0.13 percent to 3.7675/3.77 ARSB=. (Reporting by Jorge Otaola and Walter Bianchi; Writing by Hilary Burke; Editing by Dan Grebler)