US stocks hit a new high Investors concerned about the merger

US stocks rose to a record high on Monday, boosted by corporate optimism over merger deals and investor bets on Republican corporate tax cuts.

Communications chip maker Broadcom (AVGO.O) said Monday it proposed to buy smart chip supplier Qualcomm (QCOM.O) for $ 70 a share in cash and stock at a deal valued at $ 103 billion, The deal will be the largest merger ever in the tech industry. Qualcomm closed up 1.15%, Broadcom rose 1.42%.

"The deal is huge," said Paul Nolte, portfolio manager at Kingsview Asset Management. "There are not many deals this year, so it may stimulate some deals before the tax policy changes."

Television conglomerate 21st Century Fox surged 9.93% after CNBC reported it had held discussions with media giant DIS.N over the sale of most of the company.

Last week, the Republican Party proposed to cut corporate tax from 35% to 20%, ending some tax breaks for businesses and individuals, which also boosted investor optimism.

"I think this is a major incentive," said John Brady, managing director of R.J. O'Brien & Associates. "Even if the corporate tax is cut to only 25% or 27%, it is still a positive move."