S&P/ASX 200 Index (ASX: XJO) stock Amcor PLC (ASX: AMC) is slipping today.

Shares in the global packaging giant closed yesterday trading for $15.70. In morning trade on Wednesday, shares are swapping hands for $15.28 apiece, down 2.7%.

For some context, the ASX 200 is down 0.2% at this same time.

Amcor shares also trade in the United States on the New York Stock Exchange. Overnight shares dipped 2.6% on the NYSE.

This comes amid big news of a $13 billion merger.

Here's what's happening with the ASX 200 stock.

ASX 200 stock expanding its horizons

Investors awoke this morning to the news that Amcor is acquiring US-based Berry Global Group Inc (NYSE: BERY).

The all stock deal is valued at a whopping US$8.4 billion (AU$13 billion).

Under the deal, Berry shareholders will receive 7.25 Amcor shares for each Berry share held upon closing. This will see Amcor shareholders own around 63% of the combined company, with Berry shareholders owning 37%.

Both company boards have unanimously approved the transaction, which values Berry at US$73.59 per share.

Following the merger, the beefed-up ASX 200 stock will rake in combined revenues of US$24 billion and adjusted earnings before interest, taxes, depreciation and amortisation (EBITDA) of $4.3 billion.

Their increased scale of some 400 global packaging plants is expected to produce US$650 million in cost, growth and financial synergies by the end of the third year of the merger.

What did management say?

Commenting on the merger news that has yet to boost the ASX 200 stock, Amcor CEO Peter Konieczny said, "This combination delivers on our strategy to accelerate growth by putting the customer first, elevating the role of sustainability and orienting the portfolio toward faster growing, higher margin categories."

Konieczny added:

We will have a more complete and more sustainable product offering, supported by stronger innovation capabilities, global scale and supply chain flexibility.

We will help global and local customers grow faster and operate more efficiently with a team of exceptional talent. As a result, this combination also drives a step change in annual free cash flow, earnings growth and value creation for our shareholders.

Berry CEO Kevin Kwilinski said, "Our combination with Amcor is a logical next step in our company's evolution, and it is a testament to our entire team that we're well positioned to build on this momentum and deliver even more value to our shareholders."

Kwilinski added, "We will be better together, and I look forward to all we will achieve as a combined organisation."

The ASX 200 stock aims to close the deal with Berry in the middle of calendar year 2025.