It's true Congress sometimes does the Lord's work, but for Sen. Howard M. Metzenbaum (D-Ohio), the church-organ tax break bill went a little too far.

It wasn't the organ that bothered him. It was the Senate Finance Committee, in the finest of ironies, had tacked an amendment onto the bill, killing the 2 percent federal excise tax on wagers placed with organized betting outfits.

The import tax break for the St. Paul's Episcopal Church in Riverside, Conn., thereupon became a centerpiece of a new legislative traffic jam in this final week of the 96th Congress.

Metzenbaum put a "hold" on that and 18 other "miscellaneous" tax measures, stationed aides in the Senate chamber to watch out and put himself on sentinel duty yesterday to prevent them from slipping to passage.

He had help from Sen. William Proxmire (D-Wis.) and several other senators who object to some of the bills, which are being shepherded by Finance Chairman Russell B. Long (D-La.), who is at his wily best at this serious game that is played every year when adjournment nears.

The objecting senators' plan is to stand constant watch on the floor through tomorrow and block any unanimous-consent requests that would send a tax bill to approval without discussion.

Constant watchfulness is the only way in the hectic final days of a Congress, when scores of measures are rushed through under unanimous concent procedures.

In the final few days of the 95th Congress, about 500 bills, some large, some small, soomed through. At one point, to demonstrate the inanity of it all, Proxmire asked for unanimous consent to abolish the Republican Party. It would have been approved had Sen. Bob Dole (R-Kan.) not rushed onto the floor to object.

"I'm not going to block any substantive legislation," Metzenbaum said, "but our process ought not to work this way, I am talking about the Christmas tree of tax giveaways. It is an incredible reality here -- it's open season for all the special interest lobby groups."

The gambling tax exemption, pushed by Sen. Howard W. Cannon (D-nEv.), is an example. It would free private betting organizations, principally in Nevada and New Jersey, from an excise tax on bets and kill the $500-per-employe registration fee they must pay Uncle Sam.

Estimated loss to the treasury: about $16 million annually.

Cloaking it in respectability, the Finance Committee added it to a House Ways and Means Committee bill freeing the Connecticut church from paying duty on an imported organ.

Cannon, no rookie at these things, took the precaution of also adding his gambling tax exemption to another bill. Metzenbaum, along with Sen. Bill Bradley (D-N.J.), put a hold on that one, too.

There are other tax goodies hovering over the chamber, with their sponsors waiting for Metzenbaum or one of his allies to lose track of events.

One, for example, which also appears in two different bills, would abolish the provision of law that now lets participants in employe stock option plans vote their stock. Employers don't want them to have acess to company books. As of yesterday, Metzenbaum still could not find out who sponsored that.

Another, promoted by Bradley, would give the National Biscuit Co. a tax break worth about $10 million by allowing write-off of certain overseas profits not now permitted.

"We've had two dozen telephone calls in the last 24 hours from lobbyists and lawyers complaining about what I'm doing to their tax breaks," Metzenbaum said.

Not only must the Ohio senator keep an eye on what he knows about. He has to worry about the unknown as well, and when it may strike.

An example: aides to Sen. Daniel Patrick Moynihan (D-N.Y.) were circulating draft language of tax amendments that might help publishers and other businesses skirt a Supreme Court ruling banning the practice of counting year-end product inventories as losses against their profits.

Alerted by the publishers, librarians were enlisted this week to contact their senators and ask for help if such an amendment reached the Senate floor.