When all of the monthly total return data for May is aggregated by fund objective, stock funds generally outperformed fixed income -- and energy and utilities sectors rose above the rest, averaging 5.39% and 3.35% respectively.

The best energy and natural resource ETF in May is the

Market Vectors Coal ETF

(KOL) - Get Report

, returning 22.04% for the month. There were unbelievable one-month returns of 90.77% in

Western Canadian Coal

(WSJXF)

, 71.35% in

James River Coal

(JRCC)

, and 67.89% in

Alpha Natural Resources

(ANR)

.

The second-best ETF fund objective for May is the utility sector. With 200% leverage to the Dow Jones U.S. Utilities Index, the

Ultra Utilities ProShares

(UPW) - Get Report

garnered 6.06%. Making up for the underperformers, electric utility

TECO Energy

(TE)

generated 28.58%, energy pipeline company

National Fuel Gas

(NFG) - Get Report

delivered 17.84%, and gas distributor

Nicor

(GAS)

rose 16.26%.

Domestic growth ETFs, led by

ProShares Ultra QQQ

(QLD) - Get Report

at 11.94%, averaged 3.12% as a group. The fund targets twice the return of the Nasdaq-100 index, which had a top-performing member in May in

Marvell Technology Group

(MRVL) - Get Report

,

Symantec

(SYMC) - Get Report

,

Activision

(ATVI) - Get Report

, and

Dell

(DELL) - Get Report

.

An interesting global equity ETF making a comeback in May is the

Market Vectors Nuclear ETF

(NLR) - Get Report

. Mining company holdings specializing in non-ferrous metals like

Aurora Energy Resources

(AUEGF)

, up 57.57%;

Ur-Energy

(UREGF)

, up 51.93%; and

USEC

(USU)

, up 50.22% celebrated a good month.

The non-U.S. equity group turned red into green, with the

Market Vectors Russia ETF

(RSX) - Get Report

adding 17.59% to an already parade-worthy year. The four largest holdings that combine to 50.2% of assets -- Lukoil, Gazprom OAO, Sberbank, and MMC Norilsk Nickel -- are making the most of Russia's increasingly centralized economy.

For an explanation of our ratings,

click here

.

Kevin Baker became the senior financial analyst for TSC Ratings upon the August 2006 acquisition of Weiss Ratings by TheStreet.com, covering mutual funds. He joined the Weiss Group in 1997 as a banking and brokerage analyst. In 1999, he created the Weiss Group's first ratings to gauge the level of risk in U.S. equities. Baker received a B.S. degree in management from Rensselaer Polytechnic Institute and an M.B.A. with a finance specialization from Nova Southeastern University.